Abstract: During June and September 2018, experiments were conducted on effect of 4,8-dihydroxy-1-tetrahydronaphthone (4,8-DHT) made from allelochemical in the Carya cathayensis on herbicidal activity in Cerasus yedoensis and Lagerstroemia indica stands in Ningbo, Zhejiang province, according to Pesticide-Guidelines for the Field Efficacy Trials (Ι): Herbicides against weeds in forest Herbicide (GB/T 17980.48-2000). The results showed that 8 days after treatment of 36 mmol/L of 4,8-DHT, Lindernia procumbens, Gnaphalium affine, Plantago asiatica, Cardamine hirsuta, Gnaphalium pensylvanicum in C.yedoensis stand could be effectively controlled, and Hedyotis auricularia in L. indica stand, with the control effect of 100%. Different concentration of 4,8-DHT sprayed at different time indicated that it had better effect at weed seed germination. Comparing the weed control effect between different stands, it was found that the weed control effect of 36 mmol/L of 4,8-DHT was different in C. yedoensis and L. indica stands.