This paper deals with impact vibration in beam system excited by periodic displacement with cosine function. The analytical model is steady impact vibration for a cantilever beam. The beam collides elastically to clamped steel of unsymmetric faces at an arbitrary point of span. Tried to analyze by applying the Fourier series method for this system with assuming force of restitution has a triangle hysteresis loop characteristics. For verification of the analytical method, experiments are performed. The analytical results are in a fairly good agreement with the experimental ones. After that tried to analyze the infinitesimal stabilities for the approximate solution by Fourier series method by applying variation equation. As the result, experimental result appear at the stable solution region in the analytical solution.