Computer modeling simulation has been developed as an important means of product development and system testing. Simulation credibility is critical to simulation results, but the procedure of credibility evaluation is usually very cumbersome. Therefore, there is a need for a proper method of simulation credibility evaluation, which can finish the work of system establishment, quantitative evaluation, qualitative evaluation and expert advice collection. This paper introduces the principle and application of DS evidence theory, and improves it for the implementation in evaluation system. With the auxiliary of convex evidence, a methodology of simulation credibility evaluation for complex product based on DS evidence theory is established. Finally, an example is showed to illustrate the concrete application of this method in the evaluation of simulation credibility.