Abstract: For the motion simulation of a barge in waves, the rigid-body based dynamics theory and the Second Newton Law is usually used in engineering practice to establish coupling motion equations with six degrees of freedom. In this article a modified strip method is employed to deduce the added mass, damping coefficients and restoring force on motions of the barge moving in regular waves. Taking heave and pitch for example, sea load and motions response are predicted for barge moving in regular waves with frequency-domain and time-domain method, and the motion response characteristics is analyzed as well.