As a continuum of ecosystem nutrient cycle, plant-soil determines the nutrient balance and system stability of grassland ecosystem to some extent. Carbon, nitrogen and phosphorus are the three main nutrient elements in the ecosystem, they participate in the nutrient cycle of the ecosystem, and play a fundamental role in the maintenance of the ecosystem structure and function, and the C, N, and P cycles within the ecosystem were transformed among plants, soils, and microorganisms. In order to explore the effect of Ligularia virgaurea on nutrient cycling in grassland ecosystem during its diffusion process, the micropatches of L. virgaurea were taken as the research object. Six density gradients were defined according to the patch density. The changes of C, N and P in grassland plants, soil and soil microbial biomass and their ecological stoichiometry of 6 different density patches of L. virgaurea were analyzed, which were D0 (0 plant/m²), D1 (43 plant/m²), D2 (99 plant/m²), D3 (163 plant/m²), D4 (332 plant/m²) and D5 (621 plant/m²), respectively. The results showed that with the increase of L. virgaurea density, the C content of grassland plant community presented an increasing trend, plant N content increased slightly and then decreased significantly, when the density of L. virgaurea was equal or greater than 160 plants/m², the plant N content decreased significantly. Plant P content decreased at first and then increased, plant C∶N ratio showed a gradual upward trend, C∶P ratio increased at first and then decreased, N∶P ratio increased at first and then decreased. The contents of C, N and P in soil increased at first and then decreased, in which C content reached the maximum at D2, and the N content of D1-D4 is higher than that of D0 and D5, but there was no significant difference among patches. P content in D3 was significantly higher than that in other patches. Soil nutrients were mainly limited by nitrogen. Soil microbial biomass carbon tended to decrease with the increase of L. virgaurea density, while the changes of microbial biomass nitrogen and microbial biomass phosphorus showed "N" shape, and MBN∶MBP showed a trend of increasing first and then decreasing. Through correlation analysis and redundancy analysis, the density of L. virgaurea was significantly correlated with C, N, MBN and MBP, Plant C content and soil C content were significantly positively correlated with MBN, and soil nutrients were more closely related to microbial biomass.