Climatic resources in Heilonggang summer early-maturing district are researched. The results show that temperature is always the most important factor in all the climatic factors in the grain number and grain weight deciding period. The second important factor is the rainfall. The comprehensive effect of all climatic factors is more greater in the grain weight deciding period than the grain number deciding period. The effect of grain weight changes is double that of the grain number. The relationships of the ear grain number with daily mean temperature, daily sunshine time,and the amount of precipitation are positive logarithmic function, positive exponential function, and negative power function. During filling period there are negative and positive linear function relationships of grain weight with daily mean temperature and daily range of temperature. The relationship of the amount of precipitation with the grain weight is quadratic cure function. Comprehensively, growing early-maturing corn breeds in this area, the rainfall is generally surplus in the grain number deciding period, but in the filling period the rainfall is generally shortage. The quantity of heat is superfluous.