In order to establish the forming limit curve of dual phase steel DP780 under uniaxial tensile pre-strain condition, the mechanical properties of high-strength steel DP780 with a thickness of 1.6 mm were tested considering uniaxial tensile pre-strain. Firstly, different degrees of uniaxial tensile pre-strain were manufactured on the large sample, and then, a small sample was intercepted at the center of pre-deformed large sample for uniaxial tensile test and the material parameters such as anisotropy coefficient, elongation after fracture and hardening coefficient were obtained. Furthermore, based on semi empirical formulas, the forming limit curve considering uniaxial tensile pre-strain was derived. The results show that the uniaxial tensile pre-strain has a significant impact on material performance parameters and forming limits. As the pre-strain increases, the elongation after fracture gradually decreases. When the pre-strain reaches 12%, the elongation after fracture decreases 35.4%. As the pre-strain increases, the forming limit point gradually decreases in the regions of plane strain and biaxial tensile strain. The forming limit curve on one side of uniaxial tension is shifted to the right due to the influence of pre-strain, but the forming limit does not change with the increasing of pre-strain. Based on two-step deformation physical experiments and prediction model, the mechanical properties of materials under specific pre-strain loads can be analyzed very efficiently, and an accurate forming limit diagram reflecting the pre-strain effect can be established, which is convenient for engineering  technologist to judge the forming performance of pre-strain plates in actual production.