Abstract: This study aimed to determine the effects of arbuscular mycorrhizae fungi Glomus mosseae and grass endophytes on the growth, nutrient absorption and phosphatase activities of Lolium perenne without phosphorus addition (P₀) and with 50 mg/kg phosphorus addition (P₅₀). Seeds of perennial ryegrass infected with grass endophyte (E⁺) and without grass endophyte (E^-) were used to establish plants with and without the endophytes. The results showed that: 1) AM fungi and grass endophytes had significant effects on the host biomass (P<0.05); plants infected by both AM fungi and grass endophytes (AME⁺) had the lowest biomass. Plants infected by only Glomus mosseae had the highest biomass under P₀, while plants free of the two symbiosis fungi reached their highest biomass under P₅₀. 2) Phosphorus addition increased mycorrhizal colonization of perennial ryegrass by 11.40%, while infection with grass endophytes inhibited plant mycorrhizal colonization by 18.65% and 11.77% under P₀ and P₅₀ respectively. 3) G. mosseae had no significant effect on the absorption of P (P<0.05). Grass endophytes increased the content of total N, while AM colonization decreased the total N of plants with grass endophytes. 4) Phosphorus addition significantly increased phosphatase activities (P<0.05). Plants infected by AM fungi and grass endophytes had the highest phosphatase activities across the treatments. Each of the two symbiosis fungi improved plant growth when taken alone; however, they showed competition on photosynthate and did not enhance plant growth and nutrition absorption when applied together.