Based on the daily meteorological data of 28 meteorological stations in Gansu Province from 1967 to 2017, the water requirement in different growth periods and the whole growth period of maize were calculated using the crops coefficient method recommended by Food and Agriculture Organization of the United Nations. Meanwhile, the effective precipitation in the whole growth period of maize was calculated by using the method established by the U.S. Department of Agriculture Soil Conservation. Thus, the water deficit was obtained. The interannual variation and spatial distribution characteristics of water requirement and water deficit in Gansu Province were analyzed by linear propensity estimation, Mann-Kendall test and spatial interpolation method. The results showed that the average precipitation, average effective precipitation, average water requirement and average water shortage during the whole growth period of maize in Gansu Province from 1967 to 2017 were 210.43 mm, 113.21 mm, 545.95 mm, and 421.00 mm, respectively. In past 51 years, the precipitation and effective precipitation in the whole growth period of maize showed a significant downward trend, while the water requirement and water deficit had no obvious change, which were normal fluctuation. In terms of space, the precipitation and effective precipitation in the whole growth period of maize decreased from southeast to northwest in general. On the contrary, the water requirement and water deficit increased from southeast to northwest on the whole. Among the 28 meteorological stations, only the effective precipitation of the Gannan and Minxian sites can meet the maize requirement water in the early growth stage in past 51 years. Other sites cannot meet the water requirement of maize at any stage of growth and require manual irrigation.