Abstract: In this paper, Ts-86 extract was tested for the protection effect on powdery mildew of cucumber and was further studied for the stability, the duration of the efficacy and the inhibitory spectrum of fungi. The results demonstrated that 50-fold Ts-86 was effective to control the disease and its efficacy was comparable to 15% WP Triadimefon 1000-fold, which reached 93.04%. The efficacy was not stable in different temperatures and pH values, but its efficacy was better in pH 6-8 and was the best after treated at 100℃ for one hour. While its light stability was very good.The duration of the protective efficacy of Ts-86 to S. fuliginea could persist 3 days. The inhibitory spectrum to fungi was rather extensive.