Changes in nitrogen (N) deposition and precipitation regime are widely recognized as key drivers of the structure and functioning of terrestrial ecosystems. Precipitation in semi-arid regions show a trend toward increasing precipitation intensity, however, how ecosystem stability responds to the combined changes in precipitation (specifically its intensity and frequency) and N addition, as well as the underlying mechanisms, remains poorly understood. This study focused on a temperate grassland in Inner Mongolia, using 8-year data from a field experiment to investigate the effects of N addition (0, 10, and 40 g N m⁻² yr⁻¹) and changes in precipitation regime (addition of 80 mm with two different intensity: 10 mm × 8 events and 20 mm × 4 events) on ecosystem stability. The results showed that N addition reduced ecosystem stability by decreasing forb abundance and species asynchrony, mediated by soil pH, highlighting the critical role of forbs in maintaining ecosystem stability. Addition of precipitation alleviated the negative impact of N addition on ecosystem stability. The mitigating effect of precipitation on N-induced instability becomes more pronounced under higher precipitation intensity (lower frequency), mainly through its stimulation of soil moisture and soil pH, which in turn enhance ecosystem stability by promoting species richness and forb abundance. Our findings emphasize the importance of considering changes in precipitation regime when predicting the effects of N deposition on grassland ecosystem stability.