Abstract: Within the Genus gaultheria L., G. forrestii Diels, G.yunnanensis (Franch.) Rehd.and G. griffithiana Wight are the most widely distributed species in Yunnan. The essential oils derived from them mainly consist of methyl salicylate, and the contents amount to 94—99%. When we undertook the synthesis of 3,3-methylene bis-(4-h)hydroxycoumarin) from methyl salicylate by M.A.Stahman's procedure, we found that during the step of forma- tion of 4-hydroxycoumarin by treating methyl acetyl salicylate with metallic sodium, it would be better to use a ratio of the ester and sodium at ten to one by weight; the reacting temperature was controlled within a range at 180—200℃, and the reaction was prolonged about two hours. By so doing, the yield of 4-hydroxycoumarin was raised from Stahman's 22% to a new leval of 30—31%.