The paper is to simulate and analyze the mechanical behavior of the clamp system of an injection molding machine. Different commercial simulation tools are combined to create complete model of the system. The flexibility of several components is included by importing a FE model generated in ANSYS. Then the dynamic characters are presented in MBS software ADAMS. The mechanical behavior of connecting bars, tie bars were analyzed and quantified in order to work out improvements. The results show that the rear link and tie bar were the weakest parts in terms of safety.