Abstract: In this paper, with P (AAID) as matrix, nano-silica packing under the action of coupling agent, synthesis a new type of organic/inorganic composite drilling fluid loss agent LJ-1.P(AAID) is prepared with monomers IA,AM, AMPS and DMDAAC and the initiator is (NH4)2S2O8 . The optimal molar ratio of monomers is obtained by orthogonal experimental method and the result shows that optimal mass ratio is m(AM):m(AMPS):m(IA):m(DMDAAC)=8:5:1:2. In addition, the optimum reaction conditions as follows: the reaction temperature 65 ℃ and reaction time is 4 h, the initiator adding amount is 1.0 % (based on the mass of monomers). The fluid loss agent LJ-1 chemical structure were characterized by FT-IR and 1HNMR;Finally, evaluated the properties of the fluid loss agent LJ-1.The results showed that the fresh water base fluid loss agent LJ-1 in the pulp quality and quantity was 1.5%, FLAPI=5.8 mL;Salt aqueous fluid loss agent LJ-1 in the pulp quality and quantity of 3.0%, FLHTHP=18.4 mL, LJ-1 has good filtration and salt resistance performance. Additionally, the micro structure of filter cake is conducted by scanning electron microscopy (SEM) and the results shows that the filter cake have a dense grid structure.