Abstract: This paper presented an analysis of dynamics of thin elastic plates in large overall motions, Based on the established dynamic equations of thin elastic plates in large overall motions and used the method of multiple scales, the internal resonance of a simply supported thin elastic plate was investigated, The conditions of causing internal resonance which the natural frequencies must satisfy are obtained, and three dimensional diagram of set of bifurcation and different diagrams of bifurcation response curves are given in this paper.