The navigation structure of the Changzhou hydro-junction adopts a four-paralleling-lane type,and the flow conditions in the approach channels are quite complicated due to its arrangement and the lock filling & emptying courses. By physical model tests and numerical computations, we study the influence of lock emptying under different downstream water levels on the flow conditions in the downstream approach channels. Considering the lock features, we propose the currently most convenient and effective non-structural measure, i.e. to optimize the locks’ operation modes so as to solve the hydraulic problems. Finally, we determine the suggested controlling downstream water levels and their relating lock operation modes based on the study, which can be used for the lock design and management.