Abstract: From 2015 to 2016, the root and root soil of 150 Plukenetia volubilis in different morbidity and non-morbidity plots were investigated randomly in Xishuangbanna Dai Autonomous Prefecture of Yunnan Province. Spore density was determined by wet sieve from the soil. The infection rate, incidence and degree of root rot was calculated by transparent staining microscopy. The relationship between root rot and the diversity of arbuscular mycorrhizal fungi, and the effects of root infection rate and spore density on the incidence and degree of root rot of P.volubilis were studied. The findings indicated that arbuscular mycorrhizal fungi on root infection rate of 90%, vines grew well, and the infection rate is lower than 13%, the vines growing weak. And arbuscular mycorrhizal fungi spore density reached 6, P.volubilis can healthy growth. When the spore density is lower than 2, P.volubilis incidence of a disease is very serious. Arbuscular mycorrhizal fungi can enhance the resistance of P.volubilis root rot and significantly reduce the incidence of this disease.