Abstract: SP700 titanium alloy is a dual-phase titanium alloy by adding β-stabilizing elements on the basis of TC4 composition, with better comprehensive properties such as high strength, high plasticity and high fracture toughness. In order to explore the superplastic deformation behavior of SP700 titanium alloy samples with different thicknesses, SP700 titanium alloy plates with the thicknesses of 0.8 mm and 2.0 mm were chosen for study, and superplastic tensile tests were carried out based on constant strain rate method at the deformation temperature of 755~815 ℃ and the strain rate of 1×10⁻²~1×10⁻⁴ s⁻¹. The superplastic deformation behavior of the samples and the metallographic microstructure near the fractures were analyzed. The results show that the best elongation of the 0.8 mm thick samples is 900% at the temperature of 775 ℃ and the strain rate of 1×10⁻³ s⁻¹, while that of the 2.0 mm thick samples is 792% at the temperature of 755 ℃ and the strain rate of 1×10⁻⁴ s⁻¹. The peak stress of the 2.0 mm thick samples is higher than that of the 0.8mm thick ones under all conditions. At the same deformation temperature, the average grain size of the 0.8 mm thick samples at three strain rates is smaller than that of the 2.0 mm thick ones. The increase of temperature will cause the transformation of α phase to β phase, and the increase of strain rate will increase the volume fraction of β phase. The present work can lay a theoretical foundation for the superplastic forming application of SP700 titanium alloy in the aerospace field.