Distribution maps of effective precipitation (Pe), crop water requirement (ETc), irrigation requirement (Ir) and their climatic tendencies during maize growth period were calculated and drawn by single crop coefficient method Arcmap spatial analysis based on daily meteorological data in 1959—2015 of 26 meteorological stations and maize growth observation data in 1991—2008 of 14 agrometeorological stations in Heilongjiang Province. The spatial and temporal distribution of maize water supply and demand in Heilongjiang Province was revealed. The result showed that the average value of Pe in Heilongjiang Province during maize growth period was 302mm, and the high value area was located in the central area, it showed an increasing trend in May and June, a decreasing trend from July to October. The average ETc was 383mm, and it was decreased first, and then increased from west to east, ETc during the whole growth period and each month showed a increasing trend except September. The average Ir was 153mm, and its spatial distribution was similar to that of ETc, Ir in the western area was larger, it decreased in May and July, and increased greatly in August and September. Irrigation should be supplemented in time in July and August to ensure maize yield. The research result provided a scientific basis for the allocation of irrigation water resource and the formulation of irrigation practice in maize planting area of Heilongjiang Province.