Withered Litters from Leymus chinensis, Stipa breviflora and Leymus chinensis + Stipa breviflora were taken as the research object. The decomposition bag method was used to measure the residual rates of different litters through a simulation experiment, and to analyze the release law of litter elements and the influence on soil properties during the decomposition process. The results showed that: (1) During the whole test period, the residual rates and mass loss rate sof different litters showed a slow-fast trend, and the decomposition rates showed Leymus chinensis + Stipa breviflora > Stipa breviflora > Leymus chinensis. The litter decomposition in the test area could be well fitted by Olson model. Decomposing 50% and 95% of different litters needed 2.79~3.15 and 12.05~13.62 years, respectively. (2) After 360 days of decomposition, the total C, N and P of different litters all showed the state of release (NAI < 100%), and the total C showed the characteristic of fluctuating release, with the release ratio ranging from 47.88% to 54.54%. Total N and P showed the characteristics of release-enrichment-release, with the release ratios of 36.34%~47.87% and 57.08%~74.71%, respectively. (3) Decomposition of different litters increased the contents of soil organic C, N and P, which increased by 1.41~1.50 g/kg, 1.27~1.40 g/kg and 0.14~0.15 g/kg respectively compared with the initial values. These research results could provide theoretical basis for the element circulation process of grassland ecosystem.