Soil organic carbon content (SOC), soil total nitrogen content (TN) and its ecological stoichiometric characteristics indicate the carbon sink efficiency and soil quality of ecosystem, and play the critical role in supporting ecosystem structure and function and mitigating climate change. Using long-term field observation data of ecological stations of the Chinese Ecosystem Research Network (CERN), this study analyzed the spatio-temporal patterns of the SOC, TN and its stoichiometric characteristics of soil, and their responses to climate change along aridity gradient. Results showed that with the aridity intensifying spatially, the SOC and TN decreased, the response sensitivity of SOC to aridity decreased and that of the TN increased. The SOC was increased along the TN increasing. Temporally, the rate of SOC and TN changes with aridity gradient showed increased with the aridity mitigating, which were negative in the aridity region and positive in semi-arid region from 2005 to 2018. The SOC and TN of Shapotou station and Erdos station were significant increased with aridity change in past more than one decade. Additionally, the response sensitivity of the SOC, TN and stoichiometric characteristics to precipitation increasing showed an "upwardly convex" pattern, which firstly increased and then decreased with the aridity gradient, but none for temperature. The response sensitivity of the SOC, TN and carbon-nitrogen ratio to changes in precipitation and temperature were as follows: the sensitivity of soil carbon-nitrogen ratio > the sensitivity of SOC > the sensitivity of TN. It is implied that the rule of the SOC, TN and its ecological stoichiometric characteristics changes in different aridity gradient region provide the scientific basis for the of ecosystem structure and function prediction under future climate change.