Objective : To understand the principle of Yishengjiansheng-jing(YSJSJ) postponing rats senility . Method: Thirty SD rats (20 month old)were randomized into two groups:YSJSJ group,fed with the food mixing YSJSJ for eighty days .Control group , fed with the normal food for the same days. 2 month old control group: fifteen SD rats of 2 month old fed with the normal food for eighty days . Cytochrome oxidase were extracted from the livers. Cytochrome oxidase activity was determined. Results : Cytochrome oxidase activity of 2 month old control group...