The phenological change during crop development period is analyzed herein with the method of the accumulated temperature threshold value during crop development and the method of the climate tendency rate,and then the changing laws of the water demands from the typical crops under various climate change scenarios in Heihe River Basin are analyzed in combination with both the control variables of both the temperature and the phenological period. The result shows that the analysis result of the phenological period change of crop obtained by both the method of the accumulated temperature threshold value during crop development and the method of the climate tendency rate is coincided with that of the reality. The growing periods of both wheat and the corn generally present the tendencies of shortening,and then the whole growing periods are shortened. Moreover, the water demand of wheat is non-linearly increased during its whole growing period,i. e. if the mean temperature rise is 1 ℃,the growing period is to start 2 d in advance and is to be shortened by 2 d with the increase of the water demand of about 1.4 mm,while the water demand of corn is non-linearly decreased during its whole growing period,i. e. if the mean temperature rise is 1 ℃,the growing period is to start 3 d in advance and is to be shortened by 4 d with the decrease of the water demand of about 0.9 mm.