Structure design of a product under complex loads not only must meet the conditions of its strength and stiffness, but also must consider the requirements of its fatigue life. Due to the lack of historical data of actual loads and stress, it is usually difficult to predict the fatigue life of product structure in life-customized design. Taking self-propelled steel bridge as an example, which is used for spoil transportation of tunnel construction in the Beijing-Shanghai high-speed railway projects, this paper presents a method of fatigue analysis for product structure for life-customized design. The approach of this work includes steps of (1) simulating actual work and load conditions of the bridge based on finite-element (FE) method, and determining risk components of the bridge, (2) analyzing the stress time history of dangerous components of the bridge, and drawing out the stress spectrum to solve the bottleneck problem of fatigue life calculation in the bridge design, (3) correcting the material S-N curves and predicting the fatigue life of the bridge based on Miner linear cumulative damage theory. The results of this research will facilitate implementation of life-customized design, thus meet the requirements of expected life of the bridge, and also improve the reliability and security of the bridge in engineering application.