【Objective】Balance between various elements in the ecosystem has been a focus or a hotspot of the researches on ecology and biogeochemical cycles under global change. Ecological stoichiometry is a science that combines some basic principles of biology, physics and chemistry, explores for balance of energy and balance of various chemical elements in biological systems and provides an integrated approach to investigating rules of the behaviors of various elements in biogeochemical cycling and ecological processes and their stoichiometric relationships. Ecological stoichiometric ratios of C, N and P are important characteristics of the process and function of an ecological system. 【Method】In order to explore variation rules of the contents of organic carbon, nitrogen and phosphorus in shoots and litter of plants and C:N:P stoichiometry characteristics during various enclosure phases of the 30 years of restoration and succession process of natural grasslands in the Yunwu Mountain, typical quadrats of grassland that had been enclosed for restoration for 1, 12, 20 and 30 years were set up for analysis of nutrient contents in shoots and litter of the plants in the grasslands and their relationships with enclosure age in the Loess Plateau. 【Result】Results showed that carbon, nitrogen and phosphorus contents in shoots and little of the plants and their stoichiometry varied sharply with enclosure age. Carbon, nitrogen and phosphorus content varied in the range of 388.1~437.6 mg g^-1, 12.13~15.42 mg g^-1 and 0.78~1.06 mg g^-1, being 418.0 mg g^-1, 13.16 mg g^-1 and 0.92 mg g^-1, on average, respectively in shoots of the plants; and in the range of 402.7~427.2 mg g^-1, 8.58~11.04 mg g^-1 and 0.49~0.56 mg g^-1, being 411.3 mg g^-1, 10.34 mg g^-1 and 0.53 mg g^-1 on average, respectively; and C:N, C:P and N:P ratio in the range of 24.91~37.37, 380.1~562.1 and 12.14~15.86, being 32.51, 473.6 and 14.64, respectively, in shoots of the plants, and in the range of 37.18~47.11, 755.5~885.9 and 16.41~22.31, being 40.71, 819.9 and 20.30, respectively in litter of the plants. In terms of average of the content of nitrogen and phosphorus shoots of the plants was higher than litter of the plants, while in terms of average of the C:N, C:P and N:P ratio a reverse trend was found. It is known that N: P ratio is an important factor that controls litter decomposition and nutrient cycling. Litter, low in P concentration was often high in N and lignin content (or in N: P ratio) and decomposed slowly, while litter low in N:P ratio decomposed easily. As litter of the plants in the grassland of the Yunwu Mountain was low in N:P ratio, it decomposed relatively fast, and kept little nutrients in storage. C, N and P contents in shoots of the plants were extremely significantly correlated with each other (p<0.01); P content in shoots of the plants was in extremely significant negative relationships with the C:N, C:P and N:P ratio (p <0.01), while C and P contents and C:P and N:P ratios in litter were extremely significantly related to P content in shoots of the plants. N:P ratio in the plants of Yunwu Mountain varied between 14 to 16. As plant growth was affected jointly by N and P, it is recommended that application of N and P fertilizers be increased in rate so as to prevent degradation, rationalize exploitation and maintain sustainable development of the grasslands. 【Conclusion】This comprehensive research shows that enclosure can increase vegetation coverage, biomass of the plants, and plant productivity of the grassland and the measure in this area can make the grassland vegetation ecosystem present a trend of comprehensive recovery. The findings of this study help further understand rules and mechanisms of the interactions of carbon, nitrogen and phosphorus on different components of the grasslands in the Yunwu Mountain.