In the process of high temperature deep well drilling，water based drilling fluid is prone to problems such as sharp increase in fluid loss and deterioration of performance，which seriously affects wellbore stability and drilling safety. Therefore，the research on high temperature fluid loss control mechanism and materials has become a critical issue in current oil and gas drilling engineering. This review summarizes the influencing factors and mechanism of high temperature fluid loss of water based drilling fluids，analyzes the synergistic effects of temperature，pressure，and formation conditions on leak off performance，and reveals the underlying mechanisms of clay particle aggregation，polymer molecular chain degradation，and mud cake structure disruption under high temperature conditions. On this basis，the research progress of high temperature fluid loss control materials in recent years is discussed，including the functional design，synthesis methods and performance optimization strategies of modified natural polymers，high temperature polymers，sulfonated materials，and nanocomposite materials. The high temperature stability and fluid loss control effect of four kinds of fluid loss reducer are compared. The problems of ultra-high temperature adaptability，environmental protection and economy are summarized，and the future development directions of extreme environment resistance，green sustainability and intelligent design synergy are prospected. This review provides theoretical insights and technical support for the development and application of fluid loss control materials for high temperature drilling fluids.

To address the common challenges of rheological deterioration，excessive fluid loss，and wellbore instability for drilling fluids under high temperature，high salinity，and high stress conditions in ultra-deep wells，a cationic nanogel viscosifier and plugging agent，P（AM-DMC），was designed and synthesized from acrylamide （AM） and methacryloxyethyltrimethylammonium chloride （DMC） via inverse suspension polymerization. This material combines the viscosity-enhancing property of flexible polymer chains with the high interfacial activity and size effects of nano-particles. Scanning electron microscopy （SEM） showed the material has an irregular polyhedral morphology and a particle size distribution of 200-500 nm. The performance of the developed material was systematically evaluated in a low solid water based drilling fluid，including rheology，filtration control，and salinity tolerance，while the contact angle and Zeta potential measurements were used to reveal the micro-interfacial properties. The material exhibited high hydrophilicity （a contact angle of 13°） and excellent dispersion stability，facilitated by its strong positive surface charge （Zeta potential of +59.1 mV），which forms the basis of the synergistic viscosity-enhancing and plugging mechanism. Results demonstrated that P（AM-DMC） significantly improves the structural viscosity and shear resistance capacity of the drilling fluid through strong electrostatic adsorption between its cationic chains and clay particles，along with the formation of a three-dimensional network of the materials. Increasing the dosage of P（AM-DMC） markedly enhanced the apparent viscosity and yield point while significantly reducing both API and HTHP fluid loss. The system maintained excellent rheological stability and low fluid loss after aging at 170°C，confirming its outstanding thermal stability. It is indicated that P（AM-DMC） nanogel is a novel additive for high-performance drilling fluids in deep complex formations，offering efficient viscosity enhancement，fine plugging，and superior temperature resistance and thus holding significant engineering value for the safe and efficient drilling of ultra-deep wells.

The global oil and gas exploration is gradually moving from shallow layer to deep layer，conventional hydrocarbon resources to unconventional hydrocarbon resources，medium and high-permeability to low-permeability and low-grade，and shallow seas to deep seas. With the increasing drilling workload，fit-for-purpose drilling fluid technology is needed to provide support for high-performance drilling. High-performance drilling fluids are the key to safe，efficient，economical，and green drilling，and the drilling fluid rheology is the core parameter for evaluating the performance of the drilling fluid system. As an essential treatment agent for building the drilling fluid systems，rheology modifiers can enhance viscosity and shear，improve the yield point-plastic viscosity ratio and optimize shear thinning，so as to control the rheology of drilling fluids. In order to drive the research and development of new rheology modifiers for drilling fluids，this paper investigates and classifies the rheology modifiers for water-based drilling fluids at home and abroad，and summarizes the research results，application，and existing problems of various rheology modifiers. The future direction of rheology modifiers for water-based drilling fluid was also analyzed to facilitate the technical improvement of water-based drilling fluids.