Enzymatic synthesis of S-phenyl-L-cysteine from L-serine and thiopheno catalyzed by tryptophan synthase from recombinant Escherichia coli were studied. The factors such as temperature, pH, molar ratio of L-serine to thiopheno and substrate concentration were investigated. The optimal temperature and pH value were 37 ºC and 8, respectively. The optimal molar ratio of L-serine to thiopheno was 1:1.2. The optimal substrate concentration of L-serine was 400 mmol/L. Under the optimal conditions, bioconversion rate of L-serine reached 91% after 16 h. The stable hydrogen bonds were formed between thiopheno and tryptophan synthase active site Ser235 and Gly233.