Abstract: The investigation of the solution treatment of hot-rolled TWIP steel of three different compositions (Fe-25Mn-4Si-2Al, Fe-30Mn-4Si-2Al and Fe-30Mn-3Si-3Al) revealed that prolonging the temperature holding time can increase the elongation with no obvious change found in strength. Because prolonging the holding time benefits both the generation of more annealing twins to increase their boundary areas and the increase in the number of CSL boundaries which are favorable for the resistance to intergranular corrosion, fracture and creep. Therefore, the mechanical properties especially the toughness of TWIP steels can be improved by way of controlling its heat treatment process to increase the number of CSL boundaries in original structure.