Abstract: Common effect of wave and slip of internal heavy loads will exacerbate rolling of the ro-ro ship. This is one of the important reasons for overturn of ro-ro ships. The floating base system is composed of a ro-ro ship and slipping heavy loads. The rolling angle of the ship and the transverse displacement of the heavy loads on deck are taken as two degrees-of-freedom. Considering the influence of the nonlinear restoration moment and nonlinear damping moment, and making use of dynamic method of multibodies system, dynamic equations of the floating base system are established. Taking a certain channel ferry as an example, numerical analysis is carried out for nonlinear rolling response of the ship and displacement response of the slipping heavy loads under common effect of synchro-slipping heavy loads and wave, and compared with linear response. Results show that the nonlinear rolling angle of the ro-ro ship increases markedly when considering the nonlinear characteristics.