In aviation kerosene hydrogenation unit, the 15CrMo steel with good resistance to hydrogen embrittlement performed obvious pitting corrosion with certain micro-cracks in H2/H2S environment. In this paper, the failure behavior of 15CrMo steel in H2/H2S environment had been studied using electrochemical method and microscopic morphology. The results showed that within 10 days, the 15CrMo steel performed good resistance with a smaller max pit depth (15.48 μm on the 10th day) in H2/H2S environment, proved by the passivation zone (-0.75~-0.62 V on 10th day). Furthermore, 15CrMo steel exhibited activated corrosion with a significantly increasing max pit depth and corrosion current density, especially, reaching 131.91 μm and 17.29 μA/m2 on 30th day. Moreover, the stress corrosion cracking caused by H2S appeared on 30th day.