Abstract: To evaluate the allelopathic potential of three diterpenes,including wangzaozin A,leukamenin E and weisiensin B,Lolium perenne L. and Lacutuca sativa L. were taken as materials and the effects of three entkaurene diterpenes on the seed germination,growth,chlorophyll,membrane damage of tested plants were studied respectively. It was found that three diterpenes with different concentrations had a slightly decrease on germination of L. perenne L. and L. sativa L. seeds,but the germination time was delayed obviously;three diterpenes at higher concentrations had significant negative effects on the root length,seedling length,fresh weight and dry weight of plants respectively,and it showed clearly concentration-dependent trend;meanwhile,the chlorophyll a and chlorophyll b contents were significantly reduced but the malondialdehye（MDA）content and relative electricity conductivity were increased,however,the relative water content showed downward trends.The results showed that three diterpenoids inhibited the growth of tested plants by affecting its photosynthetic capacity,causing oxidative damage to the cell membrane and reducing the water retention of the leaves.