The cargo volume of Changzhou hydro project has leapt to the first place in the world’s natural waterway. However，the descending trend of the low water level downstream the hydro-project causes a sharp decline in the navigation assurance rate of the first and second ship locks，which restricts the overall carrying capacity of the hydro-project. Based on the hydrological data and the results of river physical model test，this paper studies the change of the carrying capacity of the first and second ship locks. The results show that since the operation of the hydro-project，the tonnage of navigable ships of the first and second ship locks generally declines，which the first and second ship locks can only pass through 500 t and 100 t levels respectively by 2019 under the design flow （1 090 m3/s in the Waijiang river）. After the implementation of the 3 000 t level navigation channel regulation project from Guigang to Wuzhou in future，only when the discharge of Waijiang river reaches 1 875 m3/s and 2 470 m3/s respectively，the national standard ship type and Xijiang ship type can pass the ship locks smoothly（the first and second ship locks）. It is an important way to comprehensively improve the overall carrying capacity of Changzhou hydro-project for deeply releasing the utilization rate of the first and second ship locks，by optimizing the joint scheduling of upstream reservoirs to increase the dry season flow and the combined scheduling of the first and second locks under different discharge conditions.