S-adenosyl-L-methionine(SAM) was a type of active amono acid,which is of broad prospects in application,and biosynthesis employing Pichia pastoris was the main manufacture method,while during the process,SAM was easily converted to glutathione(GSH),which could be further converted to glutathione oxidized(GSSG).The present study analyzed the dynamic changes of total GSH levels,and revealed the relationship between Redox potential and GSH flux,on the basis of analysis of the ratio of GSSG to GSH.Later,the antioxidant Vitamine C was added,the flux from SAM to GSH was reduced and cell acticity was improved.Consequently,SAM productivity was further elevated.