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The stress corrosion cracking (SCC) behavior and mechanism of M152 and 17-4PH high-strength steels in high Cl^- environment were studied through neutral salt spray test and slow strain rate tensile (SSRT) test. The result shows that M152 and 17-4PH steels exhibit a certain sensitivity to SCC in Cl^- environment, elongations of them both decrease with the increasing time of early neutral salt spray test, and the SCC sensitivity gradually increases. Comparing the fracture morphology with lateral crack through SEM, it can be found that the fracture mechanism of M152 and 17-4PH high-strength steels converts ductile fracture to brittle fracture as the extension of neutral salt spray test time. The synergistic effect of anodic dissolution (AD) and hydrogen embrittlement (HE) result in the occurrence of SCC in high Cl^- environment, and Cl^- can promote the AD process. Due to the obvious effect of HE, 17-4PH steel has higher SCC sensitivity than M152 steel with the same time of early neutral salt spray test. 17-4PH high-strength steel is more prone to SCC than M152 in high Cl^- environment.