A new passive vibration control strategy has been put forward and applied to a cantilever beam in this paper. For the beam under principal resonant harmonic excitations, a steel ball was inlaid in its interior closed cavity without any restricts, constructing an impact system. For the system, a spring-damping impact model was employed to simulate impacts between the beam and the steel ball, and dynamic governing equations ware derived. Numerical simulations show that the amplitude of the beam vibration response is significantly reduced by the impact damping of the steel ball, and moreover, the vibration response isn’t periodic but quasi-periodic due to impacts. The self-adaptive characteristic of the steel ball is fully demonstrated by assuming that the ball impacts the beam on a virtual location instead of the actual location observed in experiments. In general, all numerical results agree with those of experiments.