The invention relates to a titanium alloy ultrasonic knife surface strengthening method which comprises the following steps: (1) machining the titanium alloy ultrasonic knife surface, grinding and polishing; (2) cleaning the titanium alloy ultrasonic knife which satisfies the surface roughness requirement, and drying; (3) putting the titanium alloy ultrasonic knife into an ion nitriding furnace, and carrying out nitriding treatment, wherein the nitriding treatment technological parameters are as follows: the pole pitch is 30-50mm, the cathode bias is less than or equal to 300V, the inside of the ion nitriding furnace is subjected to argon gas scrubbing for oxygen removal and vacuumized to the vacuum pressure of less than 5Pa, the gas medium filled in the ion nitriding furnace is NH3, the gas flow rate is 300-400 L / h, the nitriding pressure is 80-120Pa, the nitriding temperature is 800-1000 DEG C, and the nitriding time is 3-7 hours; and after the nitriding treatment is finished, carrying out furnace cooling on the titanium alloy matrix in an argon environment to room temperature, and discharging. Compared with the prior art, after the treatment of the technique, the hardness is enhanced by 2-3 times as compared with the titanium alloy matrix which is not subjected to ion nitriding treatment, and the abrasion resistance is enhanced by 8-25 times. The titanium alloy ultrasonic knife surface treated by the method has the characteristics of high abrasion resistance, high oxidation resistance and favorable high-temperature stability.