Abstract: One optimization method of acquiring the time environmental factor was proposed which made full use of the failure data from the same kind of products or the similar products in their development tests based upon the AMSAA model, One genetic algorithm method was used to the optimization process of acquiring the time environmental factor, the steps of the process were listed, and at last one practical application example was given. The research result indicated that the reliability evaluation result according to this method was nearer to the reliability level of the product in its practical use. And this method offers one reasonable way for integrated reliability evaluation using the failure data in product's development stage.