Complex mechanical products involve many specialized fields such as machinery, electronics, hydraulics, and computers, so their initial cost is usually higher. In addition, regular and irregular maintenance are also needed to extend their service life, so that the cost of the product in its life cycle will be increased. Therefore, for the manufacturing enterprises of complex mechanical products, it is very important to achieve the best matching between reliability and economy. In order to survive in the fierce market competition, it is necessary to compare with other similar products in the market, so as to clearly understand the level of their products, find out the gap, and improve it. However, the existing product reliability assessment methods based on probability and statistics theory cannot provide such help for them to solve this problem. Therefore, this paper puts forward a method to evaluate and improve complex mechanical products by using a data envelopment analysis (DEA) model considering the reliability and economy of product comprehensively. Through the relative effectiveness of DEA, the same type of products on the market can be compared, providing specific method for enterprises to evaluate and improve their own product level to achieve the best matching of economy and reliability. This paper introduces the principle and steps of this method and takes the hydraulic component manufacturing enterprise as an example to carry out practical research, which verifies the feasibility and effectiveness of this method.