Stress corrosion cracking (SCC) of non-sensitized austenitic stainless steel during immersion of MgCl2 solutions was investigated by X-ray computed tomography and scanning electron microscopy. SCC cracks propagated transgranularly at the initial stage, and switched to the IGSCC mode under the nominal stress of 120 MPa. No dimples were present on the SCC fractography, but numerous cleavage facets, slip bands and pits emerged. The cohesive zone appeared ahead of the crack tip. It is indicated that the high-load SCC also coincides with the cleavage dissolution mechanism, predominantly originating from the corrosive environment particle assisted cleavage and the obstacle induced dislocation pinning.