Abstract: As a special skate board, the vigor board can move forward byswing and twisting of the body of user. In this paper the dynamicprinciple of the motion of vigorboard is analyzed. The friction forces on wheels acted by the ground producean impulse effect when the front and rear broads rotateperiodically as a result of body's motion. The formula to calculate theaverage impulse force is derived, and the zigzag of trajectory is explained.