The credibility is the lifeline for warfare simulation. To execute verification, validation and accreditation (VV&A) is an important approach to insure the credibility of warfare simulation system all the life circle. A proper method is the precondition for credibility evaluation. On the basis of analysis and comparison with existing evaluation methods, the subject integrated judgment method was put forward, aiming at the characteristics of giving prominence to the function of subject matter expert (SME) in the credibility evaluation for warfare simulation. Furthermore, a method of quantitative weights calculating based on SME was designed as the focal part of the research. These methods were applied in credibility evaluation of the warfare simulation system. The practice shows that the research is highly effective for complex system simulation, such as warfare simulation system.