To clarify the effects of enclosure on the carbon exchange of patchily degraded alpine meadow ecosystems, this study selected the degraded alpine meadow in the source area of the Yellow River on the Qinghai-Tibet Plateau for enclosure experiments. Four enclosure durations (1, 2, 5, and 11 a) and a normal grazing control were set up to investigate the response of net ecosystem carbon exchange (NEE) and its components to different enclosure durations. The results showed that after 5 a enclosure, the gross primary productivity (GPP) and ecosystem respiration (ER) of the degraded alpine meadow were significantly higher than those of the normally grazed meadow, 1, 2, and 11 a enclosure, while the NEE of the degraded alpine meadow after 2 and 5 a enclosure was significantly lower than that of normalized grazed meadow, 1, and 11 a enclosure (P<0.01). The response of other NEE components to different enclosure durations was inconsistent. The proportions of autotrophic respiration (Ra), root respiration (Rr), and heterotrophic respiration (Rh) in ER differed significantly among different enclosure durations (P<0.01). In addition, soil temperature had a quadratic relationship with NEE and exponential relationships with ER and other respiration components except Rh. Soil water content had linear relationships with NEE, GPP, ER, soil respiration (Rs), Ra, and Rr (P<0.05). Total nitrogen, total phosphorus, biomass, NEE, and its components showed significant correlations amont them. The results indicate that 5 a enclosure can significantly improve soil nutrient content and the carbon sequestration function in the degraded meadows, and maintaining their original productivity, without the need for long-term enclosure.