Increasing input of nitrogen (N) and phosphorus (P) into the grassland ecosystems induced human activities, may have effects on soil organic carbon (SOC) cycle. However, how soil microbial respiration (Rs) and its temperature sensitivity (Q₁₀) respond to N addition and increasing P availability remains unclear. Here, we collected soils from the long-term simulated N deposition site in a temperate grassland in Duolun, northern China (0, 50, 100 kg N hm^-2 a^-1), and then added available P before laboratory incubation at two constant temperatures (10℃ and 15℃) to investigate how N addition and P availability affect Rs and its Q₁₀. The results showed that N addition significantly decreased muramic acid content but increased fungal richness. In the N50 and N100 treatments cumulative respiration was significantly reduced by 61.2% and 67.1% than N0, but Q₁₀ was increased by 32.7% and 50.8% compared to the N0 treatment. However, increasing P availability had no effects on cumulative respiration and its Q₁₀. The results of stepwise regression analysis showed that fungal richness and pH were the most important influencing factors of cumulative respiration and its Q₁₀, respectively. These results suggest that N addition inhibits Rs and reduces SOC loss, but increases the sensitivity of response of SOC decomposition to elevated temperature in the Duolun grassland ecosystem, which may increase CO₂ emissions via SOC decomposition under the continuously warming scenario.