Abstract: Abstract: Crop effective precipitation and water requirement are the basis for farmland water management and irrigation. Based on the observation data from 104 meteorology stations during 1961-2010 and phenology data of maize from 17 agrometeorology stations during 1981-2010 over the maize growing regions of Sichuan basin, the effective precipitation of maize of the whole growing period and different growth stages during 1961-2010 in Sichuan basin were estimated by using the reference crop evapotranspiration and precipitation ratio method recommended by Food and Agriculture Organization, and the water requirement of maize also were estimated by using FAO Penman-Monteith equation and crop coefficient method. Further, the water deficit and water budget index in each growth stage of maize were analyzed in the study area. The results showed that the spatial distribution characteristics of effective precipitation of the whole growing period and different growth stages of maize were all significant which were higher in the southwest and northeast areas and lower in the central areas except the growth stage of sowing to jointing. The effective precipitation of the whole growing period and different growth stages of maize decreased over the past 50 years except the growth stage of milky-to-maturity. The change trend of effective precipitation of the whole growing period was between -15.2 to 3.9 mm/10a. The change trend of effective precipitation of the whole growing period was between -15.2 to 3.9 mm/10a. The spatial distribution characteristics of water requirement of the whole growing period and the stage of sowing to jointing were significant which were higher in the west areas and lower in the east areas. The spatial distribution characteristics of water requirement of the stage of jointing to milky were higher in the northeast and west areas and lower in the south areas. The spatial distribution characteristics of water requirement of the stage of milky to ripening were higher in the south areas and lower in the north areas. The water requirement in each growth stage declined over the past 50 years. The change trend of water requirement of the whole growing period was between -12.0 to -0.3 mm/10a. Except during the growth stage of milky to ripening, the spatial distribution characteristics of water deficit of the whole growing period and different growth stages of maize were all significant, which were higher in the north and lower in the south. The water deficit of the whole growing period and the growth stage of jointing-to-maturity decreased over the past 50 years. The change trend of water deficit of the whole growing period was between -10.0 to 8.4 mm/10a. Comparing the water budget index of maize of the typical stations in different study regions, the water deficit was the most serious in the northern basin and the lightest in the western basin. By compare the water deficit of different growth stages of maize, the water deficit of the most serious occurred in the growth stage of sowing-to-joining. This research can provide the basic scientific support for better use of water in agriculture and reasonable irrigation in maize growing regions in Sichuan basin.