Floating bodies are widely used in the field of offshore engineering. Existing studies show that the motion responses of a floating body in waves will change with the internal water in the cabins, and it is essential to analyze its hydrodynamic performance under various potential operating conditions. However, most of the research only considers the interaction between the floating body and the internal water in the upright position, and there has been little research on the inclined floating body caused by water partially filled in the broadside. In this study, a floating body with a plurality of longitudinal and transverse cabins was designed. The regular wave model test was carried out in a wave basin, and the numerical results were compared with the experimental results, which verified the accuracy of the model. The effects of wave direction, wave frequency, water-filling depth, and cabin division on the motion responses of the floating body are analyzed. The results show that the water inside the cabins has a significant impact on the roll motion. With the increase of the water-filling depth, the natural frequency of the roll motion decreases. Special attention should be paid to the impact on the wave direction and cabin division on the partially water-filled inclined floating body.