In order to reduce the surging acceleration of ocean fishing boats and improve the comfort of crews, based on the theory of regular wave and irregular wave potential flow, the six-Degree-of-Freedom (6DOF) motion performance, wave excitation forces and seasickness incidence of crew before and after modification of an ocean fishing boats were predicted and analyzed by panel method. The forecasting results show that the motion range of the modified fishing boats is obviously reduced and the seasickness incidence has been significantly improved.