Abstract: The stainless steel pull rod of a prototype vehicle broke during standing after 24 hours of assembly, the fracture location is at the welding joint of the stainless steel pull rod. The failure causes of stainless steel pull rod were analyzed using macroscopic observation, scanning electron microscope analysis, chemical composition testing, metallographic analysis and hardness testing. The test results show that the failure mode of stainless steel pull rod is hydrogen embrittlement fracture, the high carbon content in the pull rod material and the appearance of martensite structure in weld seam and heat affected zone during welding process are the root causes of hydrogen embrittlement fracture.