The growth and development of crops would not be separated by comprehensive climatic factors, such as temperature, precipitation, sunshine and others. To some extent, the behaviors of the climate factors have great affection on the climatic suitability of crops. In order to achieve the quantitative assessment of climate factors, the decision support system for quantitative calculation on climate suitability of major crops in Hebei province such as winter wheat, corn and cotton, has been established. Developed by Microsoft Visual Basic 6.0 language, and program design built in modular structure, the system was included by three modules following as the database of climatic suitability over the stages of crops growth and development, calculation of climate suitability degerees and decision-making services. Using the differene periods such as ten days, month, season, crop growth period as the unit, the quantity changes of temperature, precipitation and sunshine would be translated into crop-climatic suitability degrees on different growth perod by membership function of fuzzy mathematics so as to achieve a quantitative assessment of climatic fators. The calculated results output adopts grid and graphic formats, and according to the results, different management decision-making information.would be chosen then .It’s shown that the analysis results of crop-climatic suitability by the system for different crops and time perods are consistent with the actual situation.