[Objective] To evaluate water resources carrying capacity and analyze the causes of overloading problems of Hangzhou City, Zhejiang Province in order to study countermeasures and improvement approaches.[Methods] Based on national trial water resources carrying capacity evaluation method, we proposed a new evaluation method considering water volume, water quality and upstream conditions. The water resources carrying capacity of 8 units (central downtown and 7 counties, cities or districts) was studied by the new method, and overloading causes were analyzed by a set of proposed indexes.[Results] The water resources carrying capacity of Hangzhou City experienced continuous improving in the past 3 years (2013-2015), the number of overloading and critical overloading units (counties) declined from 7 to 2. There were four reasons for the overloading and critical overloading problems:① total water consumption difference among 8 units enlarged due to rapid urbanization, ② water demands increased by modern urban lifestyle, ③ insufficient self-purification capacity in river network plain, ④ relatively low efficiency of water utilization in some upstream units (counties).[Conclusion] Water resources management policies and measures should be improved in aspects of protection, rectification, restriction and supervision in the overloaded areas.