Usually the test of armament evaluation costs a large sum of money. Based on Bayesian theory, a small sample test to reduce expenses and improve economical use of the project is designed. Test load can be calculated by introducing binomial distribution in Bayesian formula. The influence of the number of additional test on evaluation can be analyzed at the same time. Furthermore, the normal route of variables and the risk of both sides can be further estimated. Therefore, a reference process helpful to evaluating pass-fail products is proposed.