With Oil and gas exploration and development in deep and ultra-deep Wells has become the main way of strategic replacement of oil and gas resources, and drilling engineering has put forward higher requirements for the temperature resistance of fluid loss reducer in drilling fluids. β-cyclodextrin has a special rigid and stable structure of pyramidal ring and a special adsorption capacity of hydrophobic inside and hydrophilic outside. β-cyclodextrin was grafted with maleic anhydride, and organosilicone polymer 3-(trimethoxy-silicyl) methacrylate with excellent high temperature stability was introduced, and copolymerized with sodium p-styrene sulfonate and dimethyldiallyl amine chloride. A high temperature resistant microsphere fluid loss reducer (LY-1) was synthesized. The optimal synthesis conditions of the fluid loss reducer are: The monomer mass fraction was 25%, the initiator mass fraction was 1% of the monomer mass, the monomer mass ratio m(C8H7SO3Na):m(KH570):m(DMDAAC):m(MAH-β-CD) was 15:3:2:15, pH was 10, the reaction temperature was 75℃, and the reaction time was 4h. The total heat loss of the polymer is about 35.98% in the range of 284°C ~ 453 °C, and has good temperature resistance at 300 °C. After adding 3%LY-1 to the 4% sodium bentonite slurry and rolling at 200℃ for 16h, the filtration loss of the slurry decreased from 140mL to 12. The polymer has good filtration loss performance, but has little influence on the rheological property of the slurry.