The environmental regulations became more and more stringent,so the demand of clean gasoline grew fast.For a long time,the catalytic cracking unit occupied a very important position in the secondary processing of crude oil in China.While olefin content of the catalytic cracking gasoline up to about 50%,it was difficult to meet the requirements of the development of clean gasoline.Based on the characteristics of fluid catalytic cracking(FCC) process,technology of improving the operating conditions and raw material conditions,changing the FCC process,improving FCC catalyst were introduced to reduce the olefin content of FCC gasoline.