It would be good and necessary that studies be made of the reliability and maintainability of a mechanical system during its whole life cycle of which the cost is an important factor affecting the performance of a product. Compared with traditional researches given separately to reliability and maintainability, this paper, based upon a previous model for the analysis of the relationship of reliability and life cycle cost, is aimed at establishing a cycle cost model of which the target is to minimize the life cycle cost of a mechanical product. And an optimal integrated model of reliability and maintainability is developed which is expected to be suitable for general mechanical products. (4 pages)