Friction of two objects or inner friction of loose materials in vibration case can present different characteristics that are different from conventional conditions. The practice shows that vibration can reduce friction coefficient and friction force between two objects, lighten abrasion of objects, reduce energy consumption and increase greatly working efficiency. The mechanism of friction in vibration case was revealed in this paper. The Curve of vibration intensity to internal friction of soil was given. The investigation indicated that friction converts from static to sliding in vibration case. The internal friction is reduced with frequency increasing and there exists the optimal vibration intensity to make internal friction least. At last, nonlinear dynamic model of vibration friction system about compaction equipment was established and its resonance response was obtained.