Abstract: Wheat cold source could clearly reduce temperature of wheat plant; it is a kind of good germplasm resource which breeds cold type wheat. The microstructure of functional leaves of cold source, cold type wheat Xiaoyan6 and warm type wheat 9430 were observed by paraffin slice method, and chlorophyll content, net photosynthesis rate, transpiration rate, stomata conductance of functional leaves were measured during wheat grain filling. The results showed that the flag leaf thickness of cold source was higher by 19.3% and 9.0% than that of cold type wheat and warm type wheat, respectively; the top 2nd leaf was higher by 19.7% and 5.7%, respectively; the top 3rd was higher by 37.2% and 2.7%, respectively. The vein transverse area of flag leaf of cold source was higher by 25.2% and 37.7% than that of cold type wheat and warm type wheat, respectively; the top 2nd leaf was higher by 5.9% and 12.6%, respectively; the top 3rd was higher by13.1% and 33.3%, respectively. The vein interval of flag leaf, the top 2nd leaf and the top 3rd leaf of cold source was higher by 17.7%, 2.0% and 9.2% than that of the same position functional leaf of cold type wheat, respectively, and lower by 3.7%、6.8% and 8.3% than that of the same position functional leaf of warm type wheat, respectively. Chlorophyll content, net photosynthesis rate, transpiration rate and stomata conductance of cold source, cold type wheat and warm type wheat were all downtrend during grain filling, but which of cold source and cold type wheat were higher than that of warm type wheat at grain-filling prophase, metaphase and anaphase.