Using Changqing oilfield distillate oil as raw material，the synthesis and optimization researches of petroleum sulfonate surfactant to flooding was carried out. Through the experimental study of fluid component -surfactant activity relationship，structure characterization of raw oil and the design and synthesis of petroleum sulfonate molecule，the vacuum distillate oil as the main raw material to produce the petroleum sulfonate，was determined preliminary，and the experiment product of petroleum sulfonate was synthesized，which could make the oil-water interfacial tension decrease to 10^-2-10^-3 mN/m at the concentration of 2000 mg/L. At the same time，the research of sulfonated process optimization was conducted ，by which the gaseous SO₃ as sulfonated agent was determined，the gas phase continuous film type as the sulfonated process to pilot production of Changqing petroleum sulfonate was utilized and the pilot product CPS-1 was obtained. The CPS-1 could reduce the oil-water interfacial tension of the MB zone in Changqing oil field to 10^-2-10^-3 mN/m at the CPS-1 concentration of 2000 mg/L，indicating that the CPS-1 had higher interfacial activity. In addition，the pH value of CPS-1 solution was 7.6-8.5，which could meet the requirements of the free alkali SP flooding to the pH value of surfactants.