Abstract: It is extremely meaningful to measure the city’s water consumption in the ecological environment, especially for maintaining ecological system, fairly using water resource and providing strategies for government departments. This paper takes the Pukou district in Nanjing city as an example, measured the changes and the influence factors of the city’s water consumption and in ecological environment in the ecological environment, bases on the MOP theory. The result showed the practical water consumption of district ecological environment is 3.5 million cubic metres; the resonable water consumption of district ecological environment is 55.072 million cubic metres; the economic benefit increases 1.041 754 4 billion RMB after adjustment. Therefore, in the theoretical and practical feasible, the adjustment of the water consumption in economical will increase the water consumption in the ecological environment.