Abstract: Response surface analysis was used to optimize the conditions in transformation of trans-cinnamic acid for PAL production by R. glutinis JM432. First,plackett-burman design was adopted to screen out the important factors affecting transformation:Span 60,PEG8000 and substrate concentration. Then,the path of the steepest ascent was utilized to approach the optimal region of transformation. At last,the optimal composition was obtained by Box-behnken design and response surface analysis. The optimal conditions of transformation were:Ammonia concentration 10 mol/L,CTAB 0.02%,Trition100 0.3%,Lecithin 0.4%,Sodium glutamate 0.5%,Span60 2.738%,PEG8000 0.274%,substrate concentration 1.193%.After optimization,the rate of transformation of trans-cinnamic acid was up to 53.22%,1.8 times higher than that in the original conditions.