Abstract: The leaf spring of a heavy truck broke abnormally during service. The fracture reasons of the spring were analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, scanning electron microscope and energy spectrum analysis. The results show that there were many corrosion pits on the tensile stress side of the spring, and fatigue cracks were initiated in the pits during the service of the spring, which eventually induced the multi-source fatigue fracture of the spring.