On the basis of the sustainable development theory of time-and-space coupling, the connotations and principles of the sustainable utilization oriented optimal allocation of water resources are analyzed systematically. In combination with the current status and the utilization trend ofwater resources in Wuhan city, the model of the optimal allocation is constituted. The methods of step by step toleration obligation and genetic algorithm are used in solving the model, the approaches and the methods of the water resources optimal allocation are explored with a guaranteed ratio of about 95% in the level year 2010 of Wuhan. The results show that: in the extremely dry year of 95% probability, the agricultural water guaranteed ratio of the whole city exceeds 90%, and in high economic growth rate-fundamental scheme the guaranteed ratio reaches 93.07%, the high economic growth rate-water savingscheme has a guaranteed ratio equal to 96.56%with only lack of agricultural water in Jiangxia and Huangpi districts; and the third industry is relatively short of water with a 85.39%guaranteed ratio in high economic growth rate-fundamental scheme and a 93.03%guaranteed ratio in the high economic growth rate-water saving scheme, while all the guaranteed ratios of other water required sections get to 100%. Compared with the forecasted values in the routine allocation, the provided model may improve the guaranteed ratio of water usage to a great extent.