Precipitation is the most important limiting factor for the processes and functions of desert ecosystems, and desert plant seedlings are extremely sensitive to precipitation changes during the growing season. In order to explore the response of desert plant seedlings to future precipitation patterns changes, we selected two typical desert plant seedlings (Nitraria tangutorum and Artemisia ordosica) in UlanBuh desert as research objects. The stoichiometric characteristics of two plant seedlings were studied with artificial simulated precipitation addition experiment, including different gradients (CK. natural precipitation, A. +25% precipitation, B. +50% precipitation, C. +75% precipitation, D. +100% precipitation) according to the precipitation of growing season (June to September). The result showed that: (1) for the distribution of C, N and P contents in different organs of seedlings, increase precipitation significantly reduced the C content of stems and C and P contents of roots of N. tangutorum seedlings, and increased C and P contents of leaves and the N content of roots(P<0.05), while it significantly increased C content in stems and leaves of A. ordosica seedlings, and decreased N content in leaves and roots and the P content in stems, leaves and roots(P<0.05). (2) For the stoichiometric ratio, the N∶P of stems, leaves and roots of N. tangutorum seedlings is relatively constant, and the ratio is greater than 16, indicating that the relative growth rate of N. tangutorum seedlings is lower under the environment of precipitation addition, and is obviously restricted by P element. However, the N∶P of A. ordosica seedlings showed a significant negative correlation with the increase of precipitation. The relative growth rate increased with the increase of precipitation. Therefore, simulated precipitation addition had a significant effect on the stoichiometric characteristics of the desert plant. Increasing precipitation is not conducive to the growth of N. tangutorum seedlings, but is more conducive to the rapid growth of A. ordosica seedlings.