Abstract: The interesterification of palm stearin( PS) and soybean oil( SO) with different mass ratios( PS∶ SO 9 ∶ 1,8∶ 2,7∶ 3,6∶ 4,5∶ 5,wt%) was catalyzed by immobilized lipase Lipozyme TL IM,and the triacylalycerols composition and their physical characteristics of corresponding fats before and after interesterification were investigated. The results showed that there is an obvious change in the triacylglycerol content of PPP,LLL,POP,PPL,PLL and PLO.The content of PPP and LLL decreased,while the content of PPL,PLL and PLO increased. For POP,its content decreased except in the case of mass ratio of 9 ∶ 1. The melting point and solid fat content( SFC) of interesterified fats decreased to a certain extent because of the declines of SSS and UUU content and the increases of SUU and SUS content,which enables these fats to be applied in producing plastic fats with different SFC requirements.When PS∶ SO were 7∶ 3,6∶ 4,5 ∶ 5,the fat content with β ' crystal increased after interesterification,which could offer ideal crystal for preparation of plastic fats,such as margarine and special fat for quick- frozen food.