The Paihekou ship lock is an important part of the Paihekou hub for diversion project from the Yangtze River to the Huaihe River. It is located at the entrance of the Paihe River into the Chaohu Lake and has complex construction conditions. Based on the existing engineering，river boundary，and related planning，a preliminary plan for the layout of the double-track ship lock is proposed.A detailed study of the navigable flow conditions in the downstream approach channel and the entrance area of the ship lock is carried out using the technical means of the fixed-bed river engineering model test. The longitudinal and transverse surface velocity and flow pattern characteristics of the downstream navigable water area when the check-gate releases flood water are analyzed. The reasons why the conditions do not meet the requirements of the specification are pointed out，and they could be improved by measures such as smoothing coastline，newly opened flood diversion channels，and control of critical and safe flood discharge. The optimized scheme can help meet the design requirements and provide technical support for engineering design and operation and management in the future.