Abstract: The posture of semi-planing ship has important influences on ship resistance.In this paper the effects of interceptor on resistance reduction of a semi-planing ship were studied through model tests.First,the model ship＇s resistance,trim and heave were determined on three typical loaded conditions without interceptor.Then added the interceptor on the stern of model ship and compared resistance and posture with the condition not ca arrying the interceptor.The height of interceptor was experimentally found to be dependent on ship speed.The results show that a well-designed interceptor can reduce the running trim and resistance of the semi-planing hull.It also shows that resistance reduction effect of the interceptor is also dependent on loading condition.The resistance reduction effect is most obvious on the fully loaded condition and it attained a maximum of 6 %.