Abstract: Before the end of the Ming Dynasty to the early of the Qing Dynasty,climate was warm,and heat energy was plentiful,so double cropping of rice in Taihu Lake basin could grow without any protection. Later the world climate entered the Little Ice Age,the double cropping of rice was extirpated nearly,grain output decreased heavily.After the Little Ice Age,although,the world climate got warm,sometimes,the thermal condition was enough for two crops but three crops one year throughout the period.So both the area and output of double cropping of rice was fluctuated with variation of cold/warm.The condition of heat energy,with the movement of climatic zone,became a sensitive factor which effects grain production.Recently,as CO₂ concentration. in atmosphere is increasing,climate is warming.With the comprehensive effect of such warming and natural cooling trend,the climate in Taihu Lake basin shows the following trend:warming in winter,cooling in summer,decreasing of annual accumulated temperature and advancing of autumn low temperature.This trend will strongly influence the grain production.