Abstract: Enclosures are one of the measures to restore degraded grassland by turning grazing grasslands into protected grasslands but the period of fencing is the key to influencing the plant community. A six year field experiment was conducted to determine the responses of community features of alpine meadow to enclosure at Tianzhu Autonomous County on the northeastern edge of the Qinghai-Tibetan Plateau. The cover, height, species diversity and biomass of the alpine meadow first increased, then decreased, and finally decreased again as the enclosure was prolonged, peaking at the fourth year. These results suggest that a 4-year enclosure is suitable for alpine meadows in the study region.