Abstract: The effects of grain size, precipitate morphology and distribution, grain boundary type on the mechanical properties and corrosion resistance of the cold-rolled Ti-Ni-Nb-Ta titanium alloy sheets annealed in the temperature range of 660-860 ℃ are investigated. The results indicate that the grain deformation of the cold-rolled thin plate is severe, and that the precipitated phase (Ti₂Ni) is distributed in long strip in the matrix. A static recrystallization process occurs in the plate in the course of annealing. When the annealing temperature is 660-760 ℃, the average grain size increases with the rise of temperature, and some of Ti₂Ni phases dissolute. When the annealing temperature is 860 ℃, the Ti₂Ni particles are completely dissolved in the matrix, and the β phase nucleates at the grain boundaries, preventing the further growth of α phase, therefore, the average grain size decreases. The yield and tensile strengths of the cold-rolled titanium alloy sheet are the highest, 691.74 MPa and 781.68 MPa, respectively, while the elongation is 9.62%, the lowest. With the increase of temperature from 660 ℃ to 860 ℃, the yield and tensile strengths decreases first and then increases, and the percentage elongation after fracture increases first and then decreases. Compared with the cold-rolled thin titanium alloy sheet, the sheet annealed has better corrosion resistance. The corrosion current density and stable current density of the titanium alloy sheet annealed at 760 ℃ are the lowest, 2.55×10^-8 A·cm^-2 and 0.36 μA·cm^-2, respectively.