Abstract:This paper studied the effects and control efficiency of high temperature on the pathoge- nicity and occurrence of Pseudoperonospora cubensis. The results showed that the P. cubensis resist- ance of cucumber was most obvious after treated at 40 ℃ for 2 h or at 45 ℃ for 1 h, with the con- trol efficiency being 58.40% and 45.81% at the forth day, and 39.35% and 37.65% at the sixth day after P. cubensis inoculation, respectively. Under high temperature, the activities of peroxidase (POD), phenylalanine ammonia lyase (PAL), chitinase (Cht), β-1,3-glucanase (Glu) in cucumber leaf were significantly higher, and large amount of lignin was deposited on the cell wall of leaf tissue, indicating that after treated with high temperature, cucumber plant manifested an induced P. cubensis resistance.