The impacts of human activities and climate change on the structure and function of terrestrial ecosystems have become increasingly obvious. In the semi-arid grasslands of China, the response mechanism of plant functional traits to these changes is still not clear. In this study, the functional traits of plant communities (CWMtrait)in Horqin sandy grassland and the average functional traits of annuals and perennials were used as the research objects. The simulation control experiment of grazing, water increase, nitrogen addition and their coupling effects in the non-growing season was carried out in August 2016. The survey and determination of plant functional traits were carried out on sandy grassland in mid-month, including plant height (height), specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen content (LNC) and leaf carbon isotopes (δ¹³C). The results showed that nitrogen addition significantly increased CWM_height and CWM_LNC (P<0.05), and decreased CWM_LDMC (P<0.05). At the same time, the coupling effect of grazing and water increase had a significant impact on CWM_SLA (P<0.05). Grazing significantly reduced the average height of annuals (P<0.05), nitrogen addition significantly increased the average height, the LNC and δ¹³C of annuals (P<0.05). Nitrogen addition significantly increased the average SLA, LNC and δ¹³C of perennials (P<0.05). At the same time, the coupling effect of grazing and water increase had a significant impact on the average SLA and LDMC of perennials (P<0.05). Showed that grazing promoted the negative correlation between SLA and LDMC, LNC and δ¹³C of plant community and perennials, and water increase promoted the positive correlation between height and SLA of plant community and perennials, as well as the positive correlation between LDMC, LNC, SLA between δ¹³C of plant community and perennials. The results showed that perennials had a strong leading role in regulating sandy grassland plant community in response to external disturbances. Grazing in the non-growing season and grazing prohibition in the growing season can be used for sustainable development and management of sandy grassland. Increased water can reduce the impact of grazing pressure on grassland plants. Nitrogen addition is beneficial to plant assimilation of δ¹³C and improves the water use efficiency of plant leaves.