Objective To study the interference forces of waves on flat-bottomed yacht. Methods The interference forces from first-order regular waves on flat-bottomed yacht were simulated and calculated based on linear slice theory and to analyze its influence on the yacht's movement. Results The effects of oblique waves on interference forces and the yacht's sidelong floating, the influence of the encounter angle (angle between the direction of wave and course) on the interference forces and its cycle, and the effect of wave frequency on the cycle of interference forces were all analyzed. Conclusion The encounter angle was a key factor of effects on the movement of flat-bottomed yacht. To keep right course, it should be necessary to adjust the encounter angle timely.