A SWATH (small waterplane area twin hull) in head regular waves was investigated by experimental method. The influences of speed and vertical position of towing point on the seakeeping performance of SWATH were analyzed. The experimental results illustrate that: the transfer functions of both heave and pitch modes depict two peak values with the increase of wave length under different speeds; with the increase of advancing speed, the peak value of transfer functions of heave mode remains almost constant, while the peak value of pitch mode changes moderately; the motion responses with the towing point at center of gravity are slightly smaller than those with the towing point at the thrust axis during all wave lengths except the resonant zone at short waves.