The invention belongs to the technical field of oil pipe preparation, and discloses a 135ksi-grade titanium alloy, a 135ksi-grade titanium alloy drill pipe and a preparation method thereof, which include, by weight percentage: tungsten: 21.0% to 25.0%, Mn: 3.0% to 5.0% %, the rest is titanium and unavoidable impurities. The preparation method includes: selecting titanium, manganese and titanium-tungsten master alloy; melting titanium, manganese and titanium-tungsten master alloy to obtain a tube blank; Extrusion molding is carried out at 960-990°C, the extrusion ratio is 17-21, and the extrusion speed is 50-60mm / s to obtain a formed pipe; the formed pipe is subjected to solution treatment, and the solution treatment temperature is 960-970°C. The treatment time is 2-3 hours; then aging treatment is carried out, the aging treatment temperature is 360-380°C, and the aging treatment time is 2-3 hours; the tensile deformation of the formed pipe after the aging treatment is preset by a percentage. The cost is 9%-11% lower than that of the existing 135ksi grade titanium alloy with the same level of performance index, the comprehensive performance of the product is improved, and the flexible thermal processing production process can be adopted to improve the production efficiency and yield.