In this paper, a new kind of filtrate reducer PAAS is prepared with 2-acrylamide-2-methylpro panesulfonic acid (AMPS), acrylamide (AM) and sodium p-styrene sulfonate (SSS) by inverse emulsion polymerization, and the optimal synthesis conditions is obtained through orthogonal experiment. And the molecular structure is confirmed by FT-IR and element analysis, which shows that the molecular structure of PAAS meet the expected design structure. And then the comprehensive thermal analysis shows that the polymer PAAS have a good thermal stability. In addition, the rheological experiments, high temperature aging experiments and fluid loss experiment shows that the drilling fluid have a good rheological properties when the adding amount of polymer PAAS is 1.5 wt%, and the FLAPI=8.4 mL before aging under 160 ℃, and the FLAPI=10.2 mL after aging. Finally, the adsorption experiment, micro structure and transverse relaxation time of filter cake shows that the filtrate reducer reduce fluid loss by adsorption.