Abstract: A preliminary study was performed on the main influence factors of the hydrolysis of racemic ibuprofen n-octyl ester catalyzed by lipase immobilized in cetyl trimethyl ammonium bromide(CTAB)/p-octyl polyethylene glycol phenyl ether(TX-100) microemulsion-based gel(MBG). The lipase immobilized in CTAB/TX-100 MBG could smoothly catalyze the hydrolysis of S-ibuprofen n-octyl ester to S-ibuprofen in aqueous solution. As the content of TX-100 in EM(the mixture of n-butanol and TX-100) increased gradually, the reaction conversion(X) always increased correspondingly, but the enantiomeric excess of produced S-ibuprofen(ee_i) decreased slightly. The curve of X vs ee_i all showed bell shape with the content of water in MBG increasing and the optimum water content of MBG was 27.3%. The influence of phosphate buffer on X and ee i was generally greater than that of water dissolving gelatin. X increased significantly in the early reaction stage(before 16 h) and then increased slowly till 24 h and didn't change any more even though the reaction was prolonged, but the ee_i decreased slightly in whoe reaction process. No significant change on X was observed in the first 3 recycle of immobilized lipase, but X decreased obviously in the following recycles. The ee i also decreased as the recycle times increased. After 10 reusage, X and the ee_i decreased by 36.55% and 0.52%, respectively.