Abstract:In order to investigate the healthgiving benefit of triterpenoids in Poria cocos peel on the inhibition a－ gainst tyrosinase and enhance both the applications of Poria peel in production and processing and its added val－ ue， the inhibition of triterpenoids from Poria cocos peel against tyrosinase was tested using in vitro biochemical enzymatic method and its mechanism was explored initially. The results showed that the inhibitory effect of chlo－ roform extract on tyrosinase was the best and chloroform was a good extraction agent； meanwhile the inhibition was irreversible.