Abstract: By using system dynamics,the SD model of water resources carrying capacity in Gansu Province is established,the main decision variables in the model are adjusted,five scenarios are designed,and the water resources carrying capacity and structural water demand are simulated and predicted. The results show that the comprehensive type 2 is the best,and it is relatively close to the general goal of the“Gansu Water Security Guarantee Plan”. According to this scenario,the variable parameters that affect economic and social development are set,and the economic scale of water resources can reach 2 575.76 billion yuan by 2035. The total water supply and total water demand are 132.35 billion m~3 and 141.29 billion m~3,the water supply and demand ratio is 0.936 8,and the structural water demand is based on the proportion of total water demand,from the largest to the smallest is farmland irrigation（70.462 6 billion m~3）,forestry,animal husbandry and fishery livestock（25.169 3 billion m~3）,industry（15.970 8 billion m~3）,urban public（13.687 7 billion m~3）,resident life（10.622 5 billion m~3）,and ecological environment（5.374 0 billion m~3）.