Abstract: Objective The purpose of this study was to research the severity of clubtoot of Brassicajuncea var.tumida Tsen & Lee under different soil pH and the relationship between the pH and clubroot of B.juncea,and provide reference for control of clubroot.Method 288 soil samples were collected from the infected fields of clubroot in Fuling District,Chongqing City,and their pH were measured.Meanwhile,the germination rate of resting spores,nutritional growth of B.juncea and clubroot incidence were measured under different pH conditions to investigate the relationship between pH and B.juncea clubroot.Result The pH of 288 pathogenic soil samples was distributed from 4.00 to 7.00.The germination rate of resting spores was higher than 50% when the pH was between 5.00-6.50,and the rates were low at pH 3.00,4.00,8.00,8.50,9.00 and 10.00.Pot experiment in greenhouse indicated that in acidic environment,clubroot incidence was significantly higher than in alkaline environment.The incidence of clubroot was serious when pH was between 4.50-6.50,and was the most serious at pH 6.00 with disease index being 84.22.Clubroot did not occur when pH was 8.00.In addition,the growth indexes of B.juncea under different pH conditions were measured.The results showed that the growth of B.juncea was sound between pH 5.00-7.50,the growth rate was the best at pH 6.50,and was inhibited at pH 4.0 and 8.00.Conclusion The clubroot of B.juncea is likely to happen under weak acidic condition (pH 4.50-6.50).The most suitable pH for the vegetative growth of B.juncea is between 6.50-7.00.In planting,clubroot of B.juncea can be controlled by regulating soil pH combining other measures.