Abstract: This study investigates the effect of nitrogen and phosphorus applications on soil nutrient cycles, focusing on soil enzyme activities in particular. Enzyme activities and available nutrients have been measured in plots of Qinghai-Tibetan alpine meadow with 4 years of N and P fertilizer application. The study focuses on six soil enzyme activities that represent several significant nutrient cycles (C, N, P, S). The results showed that the contents of available phosphorus and alkaline nitrogen increased under the different treatments. The activities of alkaline phosphatase, urease, chitinase and cellulase vary significantly under the different treatments, while there is no significant difference in the activities of arylsulfatase and sucrase. In soils at a depth of 0-10 cm, nitrogen applications have a positive effect and phosphorus applications a negative effect on alkaline phosphatase activity. Urease activity is repressed in 0-10 cm soils under both nitrogen and phosphorus treatments. In soils at a depth of 10-20 cm, chitinase activity is significantly promoted by nitrogen and phosphorus applications, and especially by phosphorus. Cellulase activity at both soil depths is repressed by nitrogen treatment. The results indicate that nitrogen supply effects the mineralization of P and that phosphorus supply can promote the decrease of N. The relative degree of phosphorus limitation may be higher than nitrogen limitation in Qinghai-Tibetan alpine meadows.