A new fluid loss additive for oil well cement was synthesized with acrylic acid (AA), n, n-dimethylacrylamide (DMAA), 2-acrylamide-2-methyl propane sulfuric acid (AMPS), acryl amide (AM), and sodium p-styrenesulfonate (SSS）, the comprehensive performance of cement slurry prepared by the new oil well cement fluid loss additive was evaluated by laboratory test. The results show that the cement slurry filtration can be controlled within 50 ml according to API measurement standard by adding this fluid loss additive and the temperature tolerance is up to 180℃. With the improved water separation resistance, longer thickening time and 36% saline tolerance, this fluid loss additive should be further widely used.