Honghua 2nd lane lock is one of the first-round key construction projects for Xijiang Golden Waterway,and it is also an important project to improve the navigation capacity of Liujiang River and Xijiang River and to achieve the goal of one-hundred-million-ton Golden Waterway.The lock chamber size is in line with the Three Gorges Lock.The working water head is nearly 20 m,and flow energy is huge.Considering the characteristics of this lock,the in-chamber longitudinal culvert filling and emptying system is chosen,and the detailed layout is put forward including a confluent culvert for improving the flow condition under single valve operation.The hydrodynamic characteristics,ship berthing condition in lock chamber,and flow conditions around inlet and outlet are all studied by a 1:30 scaled physical model.Based on the model test,recommended valve opening patterns are put forward under which all the parameters can satisfy the needs of codes and design.