Based on the research methods that simulated warming effect on plants of tundra plan (ITEX), we used four kinds of plants at alpine Kobresia humilis meadow: K. humilis, Elymus nutans, Oxytropis ochrocephala, Gentiana straminea, set a big(OTC1) and a small(OTC2) warming room, to determine the carbon, nitrogen and their stability isotopes(δ¹³C,δ¹⁵N) content changes after three years of warming. The result showed that: in addition to the C/N ratio of K. humilis was reduced by 14.1% in small warming room (OTC2), the C/N ratios of the other three species were all increased in the two warming rooms than that in the control, while the differences were all not significant(P>0.05). The δ¹³C of the four kinds of plant leaves was between -24.12 ‰ ~ -28.34 ‰, the δ¹³C of K. humilis leaf was increased with raising temperature, while the δ¹³C of O. ochrocephala and G. straminea was reduced with the raising temperature. The δ¹³C change of K. humilis leaf reached significant level(P<0.05).The δ¹⁵N of K. humilis and G. straminea were all increased in the two warming rooms than that in the control, the δ¹⁵N change of G. straminea reached significant level (P<0.05); the δ¹⁵N change of E. nutans reduced 18.7% and 26.9% in OTC1 and OTC2 respectively, while the differences were all not significant (P>0.05); the δ¹⁵N change of O. ochrocephala was reduced by 11.0% in small warming room (OTC2) than that in control, while increased by 2.8% in big warming room (OTC1) than that in control. It is observed that the carbon, nitrogen and their stability isotopes (δ¹³C,δ¹⁵N) of different functional group of plant species have different response patterns and rules to shortterm warming.