Abstract: The failure causes of the bolts of inlet valve cover of feed gas A compressor of light hydrocarbon station in an oilfield was investigated by the analysis of fracture morphology, chemical composition, microhardness, microstructure and stress condition. The results show that the fracture mode of bolts was fatigue fracture, and fatigue cracks originated from the thread root. The thread root had some defects such as notches and pits due to improper processing; the positions of defects generated stress concentration easily and became the fatigue crack initiation. Micro-cracks propagation occurred under the interaction of alternating stresses during the operation of compressor, and bolts eventually fractured. It was recommended to introduce residual stresses on the surface of thread root by surface peening, carburizing or nitriding, to carry out quenching and tempering heat treatment strictly following heat treatment requirements of high strength fastener, to tighten bolts strictly following operating requirements of compressor, and to inspect and replace bolts regularly.