The invention belongs to the field of fungi for plants, and particularly relates to a method for improving the content and yield of total flavonoid of clematis plants by using arbuscular mycorrhizal fungi. By inoculating the clematis plants with glomus mosseae under different contents of nitrogen (N) and phosphorus (P), the growth, the physiological and biochemical characteristics and accumulationof total flavonoid of the clematis plants are influenced, and by utilizing a qRT-PCR technology, the expression characteristics of responses of key enzyme genes to different contents of N and P in the synthesis pathway of flavonoid biomass are analyzed, so that influence mechanisms of the fungi on the growth of the clematis plants and accumulation of active ingredients are found, and a basis is provided for the application of the arbuscular mycorrhizal fungi in the cultivation, resource development and utilization and other aspects of medicinal plants.