To study the effect of pre-deformation on martensitic transformation and microstructural evolution in transformation induced plasticity (TRIP) steels, and to investigate the forming ability of TRIP steels, the TRIP590 steel plate was selected as the testing material, and pre-stretching in the range of 0~0.12 was applied on two sizes of specimens (standard specimen and wide specimen). Tensile testing and microstructure observation were conducted on the pre-stretched specimens. The effect of pre-stretching on the anisotropy and bulging properties of wide specimens was analyzed. The results show that pre-stretching causes a certain degree of martensitic transformation in TRIP steel, and a larger pre-stretching produces more dislocations, bringing in increase in material strength and decrease in plasticity; The highest product of strength and elongation is obtained at pre-stretch of 0.02; The larger pre-stretch also has an effect on material anisotropy, and elongation of the 90°-oriented specimen is a litter higher; the peak load and cupping value gradually decrease with increase of pre-stretch. Moderate pre-stretching can improve the overall performance of the TRIP steel, while excessive pre-stretching reduces its formability, which provides reference for structure design and formability of TRIP.