Abstract: The pitch and heave motion range of high speed light wave-piercing catamaran (WPC)in head sea would become much higher while wave length near the ship length.Theoretical approaches together with model test were induced to provide a longitudinal motion performance improvement for a 250 t W PC using hydrofoils.The influence of the hydrofoils parameters，such as the shape，size and mounting locations，were investigated.A comparison of numerical calculation results and test data suggests that the strip method，with hydrodynamic interactions between hydrofoil and the hull taken into account，is applicable to the longitudinal motion prediction of W PC with hydrofoils，though the calculated RAO is a little bigger which near the RAO peak value.Based on the model test data，the significant amplitude of heave and pitch of the tested model in head sea reduced 20％-30％ with the hydrofoils installed.