Plant diversity is an important indicator of community succession processes. The change of community plant diversity during restoration succession processes of high mountain meadow in Naqu County, Tibet, 31°30′56.2″～32°06′18.5″N and 91°55′15.5″～92°16′51.4″E, was investigated. Five sampling sites with similar physical conditions but different succession stages were selected. The method of spatial changes in place of temporal changes was applied for field survey and data analysis. During repair work on the Qi-Zang Road at various times since 1973, traffic was diverted directly onto the adjacent grassland. Each time that the repair work was finished, the grassland began to recover from the trampling disturbance. The selection of sampling sites was dependent on the reconstruction of this road during 1973, 1984, 1991～1996 and 2004, which represent restoration years of 30, 20, 10 and 0, respectively. Grassland within animal pens was selected for comparison. The investigation was conducted in August of 2004 when the vegetation was most abundant. The plant species, the vegetation coverage, the number of tillers, the frequency, the height and the weight were investigated.
Thirty-three plant species belonging to 12 families and 23 genera were found in the inventoried quadrates during the recovery process. About 48% seed plants of the total species were Leguminocae, Gramineae, Compositae and Rosaceae, and suggested the high-plants in four big families play important roles in natural vegetation recovery, while Kobresia play an important role in ultimate-communities. The plant species components changed with each succession stage. The plant species were mainly annual and biennial during the early succession stages, perennial species during the middle succession stages and predominantly Kobresia humilis during the late succession stages. Potentilla bifurca and Potentilla tanaletfolia were both found during all five stages. The accumulated number (y) of family, genus, and species during the succession process varied quadrically with the stages (y=a+bt+ct²). Moreover, the increase rate of plant species during the early period was high, and about 48% of total species recovered in the first 20 years.
The plant diversity (y) of Simpson index, Shannon-Wiener index, Margalef index, Pielou index and Complex index during the succession process varied logistically with the stages(t), (y=a/(1+e^{-（t-t₀）/ b}). The plant diversity was low during the early stage, higher during the middle stage, and highest during the entire late stage.