Abstract: The chaotic motions of axial compressed nonlinear elastic beam subjected to transverse load were studied. The damping force in the system is nonlinear. Considering material and geometric nonlinearity, nonlinear governing equation of the system was derived. By use of nonlinear Galerkin method, differential dynamic system was set up. Melnikov method was used to analyze the characters of the system.The results showed that chaos may occur in the system when the load parameters P₀ and f satisfy some conditions. The zone of chaotic motion was belted. The route from subharmonic bifurcation to chaos was analyzed. The critical conditions that chaos occurs were determined.