Based on the meteorological record of selected 616 weather stations in China during 1975—2004,reference evapotranspiration(E_T0) was calculated by using the Penman-Monteith equation recommended by FAO,and the wetness index was also estimated from precipitation and E_T0.According to wetness index values:0.03,0.2,0.5,1.0,China was classified into five climate zones:extreme arid,arid,semi-arid,semi-humid and humid zones respectively.The geographical distribution as well as time trend and variation of wetness indices in China are given and its inter-annual and decadal variations are discussed in this paper.Results show that significant wetting trend occurred in northwest Xinjiang District and southwest China,the significant drying trend was found in east Qinghai Province,south Gansu Province and north Sichuan Province.The variations in wet/dry conditions gradually became greater from eastern China to western China,with the smallest change in southwest China.1980 was a transitional year from when the climate turned from a drying trend to a wetting one.From the beginning of 1975,decadal changes were evident in that semi-humid and humid regions,semi-arid and humid regions expanded,and semi-humid ones shrank.