Abstract: Antifungal activity of the novel fungicide pyrimorph,(E)-3- morpholine,was investigated.The results of bioassay of pyrimorph against plant pathogens in vitro proved antifungal activity of pyrimorph in inhibiting the mycelium growth of Phytophthora infestans,Phytophthora capsici,Rhizoctonia solani and in inhibiting the zoosporangia gernination of Pseudoperonospora cubensis.The EC50 values were 1.38±0.06,0.72±0.05,4.44±0.03 and 5.33±0.05 μg/mL,respectively.However pyrimorph showed a weak inhibition against Fusarium oxysporum f.sp.vasinfectum,Macrophthoma kawatsukai and Gibeberlla zeae etc.The control efficacy of pyrimorph against tomato late blight,when applied 1 d,3 d and 8 d at the concentration of 400 μg/mL before inoculation with zoospore suspension of Phytophthora infestans,were 94.2%,90.8% and 78.1%,respectively.It indicated that pyrimorph had excellent preventive efficacy and persistence activity against tomato late blight.