A pot experiment was conducted to investigate the effects of AMF on the growth, P concentrations and N∶P ratios of clover and ryegrass grown in monoculture or in mixture at different P levels. The results showed that: (1) the inoculation with Glomus mosseae significantly increased dry mass and P concentration, decrease N∶P ratio of clover, while had no significant influences on those of ryegrass; (2) at different P levels, AMF had a more significant influence on P concentration of clover grown singly in soil with medium or high P than that in soil with low P, suggesting that Glomus mosseae had a different effect on P concentration of clover at different P levels; (3) ryegrass showed competitive advantages against clover in mixture, thus, ryegrass in mixture had a higher P concentration and dry mass than clover, however, the inoculation with Glomus mosseae enhanced dry mass and P concentration of clover, while decreased dry mass of ryegrass in mixture culture, which indicated that root colonization can improve the competitiveness of clover in mixture, and affected plant community structure. In addition, the colonization of Glomus mosseae also reduced N∶P ratio of clover, this can lead to the shift in limitation from P to N nutrient.