The decomposition of plant litter is jointly regulated by environmental and biological factors. However,considerable uncertainty remains on how climate change may modify the effects of species mixing on litter decomposition. Using open-top chambers to create conditions of higher temperatures and litter bags to investigate decomposition processes, we examined the effects of warming on mass loss and nutrient dynamics of the leaf litter of Artemisia ordosica, Leymus secalinus, and their 1:1 mixtures (on a mass basis) in first 150 days of decomposition in the Mu Us Desert. Warming resulted in 7%, 7.6%, 12%, 8.8%, 20% and 10% decreases in the residual rate of litter mass, C, N, P, cellulose and lignin, respectively, for L. secalinus. In contrast, warming led to 2.2%, 2.2% and 0.8% increase in the residual rate of litter mass, P and lignin, respectively, and 1.1%, 2% and 2.5% decreases in the residual rate of C, N and cellulose, respectively, for A. ordosica. Compared to separate decomposition, the residual rate of mixed litter mass, C, P, cellulose and lignin increased by 7.7%, 8.2%, 4.1%, 3.9% and 5.9%, respectively; while the residual rate of N by 4.1%. Warming resulted in 16.9%, 18.8%, 11.4%, 18.5%, 21.5% and 21.1% increases in the residual rate of mixed litter mass, C, N, P, cellulose and lignin, respectively. Therefore, antagonistic litter-mixing effects occurred during the early stage of decomposition, resulting in lower mass loss than that under separate decomposition. Furthermore, antagonistic litter-mixing effects were enhanced under warming conditions. Our findings suggest that the interactive effects of warming and species mixing on litter decomposition should be considered in predicting the biogeochemical cycling in shrubland-steppe ecosystems of the Mu Us Desert under the background of ongoing climate change and vegetation restoration.