Aimed at the outstanding problem of adjustment of filtration property and high temperature stability of high temperature water-based drilling fluid at home and abroad,the anti 240 ℃ and salt tolerant polymeric filtrate loss reducer HTP-1 was developed based on optimum design of molecular structure and selection of monomer.The optimum synthesis conditions of HTP-1 was as follows: pH value was 7.0,the mass ratio of DEAM,AMPS,NVP,DMDACC was 6∶ 3∶ 3∶ 1,the initiator content was 0.1%,reaction temperature was 60℃ and reaction time was 4 h.the result of thermal gravitational analysis showed that the thermal decomposition onset temperature of HTP-1 was up to 320℃,indicating that HTP-1 possessed strong thermal stability.The experiments of calcium and salt tolerance showed that performance of HTP-1 in drilling fluid containing 267 g/L salt or 5 g/L calcium chloride was stable,which was similar to that of the foreign anti high temperature polymer Driscal and superior to domestic metallic ion fluid loss additive PMHA-Ⅱ.The filtration reducing ability of HTP-1 at high temperature of 240℃ was better than that of Driscal(240℃) and domestic PMHA-Ⅱ(220℃) in fresh water drilling fluid,weighted fresh water drilling fluid,saturated brine drilling fluid and compound salt water drilling fluid,respectively.In the end,the mechanisms of heat and salinity tolerance and filtrate loss reduction of HTP-1 were probed.