In order to assess the effects of meteorological conditions on growth and yield of maize scientifically and quantifiably,Northeast China was taken as an example using fuzzy mathematics to establish suitability functions for temperature,moisture and sunshine,combined with the biological characteristics of maize and agricultural meteorological business services index. As a result,the climatic suitability of maize was calculated by geometric mean formula. Considering the objective differences in influence intensities on growth of maize by weather conditions,the correlation analysis was used to calculate the weight for each ten - day to every growth stage. Then the climate suitable index of maize from sowing to any stages of development in growth period was built by weighted average method. Through the uses of historical maximum,minimum and average climate suitable index,different grades climate suitable evaluation indexes were set up,by which the Climatic suitability indicators of every growth period were divided into four grades and the correlation between climatic suitability grades and yield of maize was analyzed from 1993 to 2011. The results showed good relations between climatic suitability grades and meteorological conditions during the growing season of maize in Northeast China. There was a significant correlation (P≤0. 05) existing between climatic suitability grades of three developmental stages (seeding to jointing,seeding to milky maturity,and seeding to maturity) and the margin of increase or decrease in yield of maize. In addition,the more related between climatic suitability grades and yield,the closer to maturity it is. The climatic suitability grades can evaluate the change of climate condition during every developmental stage and reflect accurately the actual fluctuations of yield year by year and the typical years of poor harvest for maize. This method is advantageous for popularization and application.