Abstract: Tensile specimens were cut from austenitic stainless steel Cr17Mn6Ni4Cu2N slab shell and core, and high temperature tensile tests were carried out on Thermorestor-W thermodynamic simulation tester to study microstructure and hot ductility. The results show that, the hot ductility in shell and core increasd with the increase of deformation temperature, and reachd the maximum at 1 250 ℃. The hot ductility of the slab shell was well, and its microstructure was fine dendrite, cracking were located in limb of ferrite dendrite. In slab core, the microstructure was composed of cellular austenitic and network ferrite, and its hot ductility was low, cracks were apt to appear in cellular austenitic. During the process of hot deformation, the cellular austenitic in slab core was easy to crack than dendrite crystal in slab shell, which leads to the low ductility in slab core.