The temperature on the Tibetan Plateau has been shown a significant increasing trend since the recent decades. Moreover, the magnitude of warming showed an asymmetric trend with significant higher warming in non-growing seasons than in growing seasons. Climate warming could have significant impact on nitrogen (N) cycling in terrestrial ecosystems. The effects of asymmetric year-round warming on N cycling are still lacking in the alpine meadow ecosystem. We carried out a simulated warming experiment in an alpine meadow to compare the different effects on the N cycle between seasonal asymmetric warming and year-round warming in the alpine meadow on the Qinghai-Tibet Plateau. The experiment was set up in July 2010, and three kinds of warming treatments, i.e. no warming, non-growing season warming, and year-round warming, were implemented using open-top chambers. Our results showed that the warming devices induced warm and dry microclimate. Both air temperature and surface soil temperature were significantly increased, and soil water content was reduced in surface soil. Warming treatment in non-growing seasons exacerbated the soil N loss, so the soil N content was decreased significantly. the Soil inorganic N content decreased by 61%, 40%, and 60% in year-round warming treatment in the early growing seasons of 2012, 2013, and 2014, respectively. Meanwhile, winter warming decreased 65% and 25% of the soil inorganic N content in 2013 and 2014, respectively. During growing seasons, soil moisture controlled soil N turnover rate which increased in the seasons with less rainfall, especially in the early growing season. The decrease in soil water content caused by year-round warming could inhibit the soil N turnover rate. The treatment of year-round warming significantly reduced soil net N mineralization during early growing season in 2013 and 2014, but promoted the net N mineralization in July and August, the peak growing seasons. The soil microbial biomass carbon showed obvious seasonal dynamics in the alpine meadow, which was lower during the growing season and higher at the end of the growing season and in the early winter season. Such variations could indicated a seasonal partitioning in the soil N utilization between plants and soil microbes to reduce the nutrient competition. Soil water content showed a parabolic relationship with the net nitrogen mineralization rate, and the peak values occurred when the soil water content reached above 14%. Regression analysis showed that soil microbial biomass in cold seasons was significantly negatively correlated with the inorganic N content in the early growing season, indicating that warming in non-growing seasons has a carryout effect. Specifically, warming in non-growing seasons was not only exerting impact on soil N cycling during the warming stage, but also exerting impact on soil N cycling in the subsequent growing seasons or even more longer time. Our results demonstrate that the change in soil N content due to non-growing season warming could affect community species composition and productivity, as well as ecosystem soil carbon and N cycles in the following growing season. Therefore, warming in non-growing seasons would have profound impact on the ecosystem processes in the alpine meadow.