Abstract: With newly designed test devices and data acquisition mode,a powdered-model-reg-ular-wave experiment of a seaplane is conducted.The changes of the experimental method can ef-fectively eliminate the negative impacts of the step-type signal mutation.Based on the test re-sults,the pitching,heaving motion and overload response variation laws with encounter frequen-cy and wavelength are obtained.The results show that the pitching and heaving motion response curve has a single peak,and the corresponding resonant wavelength varies from 1 .5 to 3 .5 times the hull length;the overload response curve has double peaks,and the first resonant wavelength varies from 1.5 to 3.5 times the hull length,while the second resonant wavelength is about 0.5 times the hull length.Based on these motion properties,the motion response of the full scale seaplane to waves is analyzed,and also some suggestions about the selection of the operational environmental condition are offered.