The drilling fluids loss reduction additive JLS-2 was synthesized by the polymeration of anti-temperature and anti-salt monomer(AMPS),acrylamide(AM),cationic monomer dimethyl diallylammonium chloride(DMDAAC) as a cationic monomer and an ester monomer(BXZ).Using API water loss as evaluation index,single factor experiments were carried out and the optimal synthesis conditions was obtained as follows,the ratio of monomer AM,AMPS,DMDAAC and BXZ was 40∶ 40∶ 5∶ 2,the total mass fraction of monomers was 20%,the amount of initiating agent was 0.30%,the reaction temperature was 70℃,the reaction time was 50 min.Infrared spectrum analysis proved that the structure of the synthesized production was identified with the original design.The performance evaluation experiments results indicated that filtration control agent JLS-2 had good capacity in depressing filtrate loss and heat resistance to 120℃,after adding 1.0% and 2.5% JSLS-2,respectively,the API water loss of freshwater mud and composite salt mud were 6.1 mL and 9.3 mL,respectively.