The impact of interannual climate variability on mean global potential vegetation distribution is investigated using the revised Community Land Model’s Dynamic Global Vegetation Model (CLM-DGVM). First two sets of regional simulations were run over 400 years in three classical climatic regions, with one driven by the cycling of 1960～1999 climate data derived from NCEP reanalysis data, and another by the climatology or repeated a single year of corresponding data. The latter didn’t contain interannual climate variability. Then two global simulations were run over 600 years, forcing by 1950～1999 climate data and the climatology respectively. Results show that interannual climate variability reduces mean global vegetation coverage, with less trees and shrubs but more grass; the global average coverage change in descending order as follows: evergreen tree, grass, shrub, deciduous tree, while the relative change rates (the ratio of global average absolute grid coverage change and coverage under climatology) increase in order as follows: evergreen tree, deciduous tree, grass and shrub. The interannual variability of precipitation has the most significant impact on the mean vegetation distribution among the six climatic factors (temperature, precipitation, wind, specific humidity, incident radiation and atmospheric pressure). Under the influence of precipitation, the difference of vegetation coverage decreases with increasing variability when annual precipitation is less than 1200 mm. Tree decreases when annual precipitation is less than 1500 mm, and the difference increases with the variability. Evergreen decreases independent with the precipitation, while the difference of deciduous tree increases with increasing variability when annual precipitation is more than 1500 mm. Difference of grass coverage is largest when annual precipitation is less than 1500 mm and its variability is moderate.