A systematic quantitative analysis is conducted,focusing on the potential capacity gap of ship locks in Xijiang River basin in the future.It supports the planning and construction of ship locks in this area.On the basis of historical data and the development trend of the economy and society,a structured method combining qualitative and quantitative approaches is used to predict the freight volume of the main channel and tributaries of Xijiang River.A system simulation modeling method is employed to simulate the operation process of ship locks and analyze their capacities.By combining the freight volume prediction with the ship lock capacity results,the capacity gaps of a series of ship locks in Xijiang River basin are analyzed.The results indicate that in 2030,there are capacity gaps of 10%,23%,32% and 55% at Datengxia,Naji,Yuliang,and Jinjitan ship locks respectively,which will be resolved once the planned projects are completed.Meanwhile,there are capacity gap of 42% at Laokou ship locks.In 2040,there are capacity gaps of 3%,19%,39%,48% and 63% at Changzhou,Datengxia, Naji,Yuliang,and Jinjitan ship locks respectively,which will be resolved once the planned projects are completed.Meanwhile,there are capacity gaps of 51% and 18% at Laokou and Guiping ship locks respectively.The capacities of other ship locks in each planning year will basically meet the freight volume requirements.It is recommended that the planned ship lock projects should follow the schedule,and the feasibility studies for the construction of new ship locks at the Laokou and Guiping hubs should be carried out.