According to the basic principle of double comprehensive effect of light and temperature and the rule of the sensitive effect of wild and cultivated soybean,we studied the changes of the index of growth and development of soybean from representative latitude during flowering period under different photperiod.The minimum difference of index of growth and development was found under 8-hour-photoperiod,the cultivated soybean flowered later than the wild soybean of same latitude.The maximum difference of index of growth and development was found under 16.5-hour-photoperiod,the cultivated soybean flowered carlier than the wild soybean of same latitude.We discussed and defined that the natural comprchensive effect of light and temperature of the region from 40°N to 35°N is the main support of evolution of cultivated soybean;that wild soybean is sensitive to photoperiod,cultivated soybean is of strong adaptability to temperature.