Abstract: Based on the daily data from 27 meteorological stations in Gansu Province during the period from 1960 to 2010, the values of evapotranspiration were calculated by applying PenmanMonteith model, and then the climate water budget was obtained by subtracting evapotranspiration from precipitation during the same period. Spatiotemporal water budget over Gansu Province was analyzed using the MannKendall abrupt test, wavelet analysis and GIS spatial interpolation means. The correlation coefficients and linear regression analysis were used to discuss the dominant factors affecting water budget. The results showed that, during the period from 1960 to 2010, the multiyear average water budget over Gansu Province varied in a range from -194 mm to -1 293 mm, it was decreased by 6.48 mm every decade, and the water loss was spatially increased from the southeast to the northwest. Water loss was gradually increased from the 1960s, decreased in the 1970s, increased continuously after the 1980s, and reached the maximum value in the first 10 years of 21 century. Average seasonal water loss was in an order of summer>spring>autumn>winter. MK abrupt test indicated that a sharp change and sensitive period of water budget occurred around 2008. Morlet wavelet analysis revealed that there were the obvious 4.87year and 4.52year periods of average water deficit over Gansu Province, which was mainly affected by the atmospheric circulation. Precipitation, sunshine duration and average humidity were the dominant factors affecting water loss.