Coastal erosion along Liaolo Bay which is a semi-circular beach and locates at the south coast of Kinmen Island was observed during past years. Field and numerical experiments were conducted to discuss the hydrodynamics inside the bay. CMS-WAVE and CMS-FLOW models were setup and validated according to the collected field data. Then, the models were applied to simulate the hydrodynamics inside the study site during typhoon events. Longshore current pattern along the semi-cicular beach is sensitive to the incident wave. For wave approaching from east direction, the most affected region inside the bay by the wave locates on the west of the beach. However, widespread impact on the whole beach was found when the wave incident from south direction. Wave (1∼2 m) travels from E∼ESE direction at the bay mouth usually occurs in winter and induces to consistently westward lognshore current along the beach with speed 0.2∼0.4 m/s. High wave approached from SE∼S direction during the studied typhoon events which induced to strong transiently and complex current patterns inside the bay beach with maximum speed up to more than 1.0 m/s. A rip circulation cell constantly found near the outcrop, which enhanced the strength of the rip circulation. Besides, rip circulation cells occasionally found at some spots along the beach respectively which depends on the incident wave energy and direction.