[Objective] The paper was to study the relationship between cytokinin and Chinese cabbage clubroot, and to explore the incidence mechanism of clubroot. [Method]The spores were extracted from the tumors of diseased plant, and their DNA was extracted for PCR test. The diagnosed spores were inoculated to the culture soils in erlenmeyer flask at seeding stage, at seed germination and 21 d after sowing, and 0.08 μmol/L 6-BA was added to the soil at germination. Spores were extracted from the root tumors developed in inoculated plants and examined by scanning electronic microscope （ SEM）, and the incidence rate of clubroot in 6-BA treatment and control was recorded. [ Result] Plasmodiophora brassicae Woron could cause the clubroot incidence of Chinese cabbage planted in erlenmeyer flasks, the incidence rate of chibroot in the treatment adding with 0.08 μmol/L 6-BA was 100%, while that in the treatment without 6-BA was 57%, and the volume of former tumor was much larger than the latter. SEM showed that the size of resting spore of P. brassicae was 1.5 -4.3μm. [ Conduslon] 6-BA applied at germination could significantly promote the formation of tumor of Chinese cabbage clubroot.
