Abstract: The effect of ultrasonic on laser deposition process in repaired components of BT20 titanium alloy was investigated by using finite element simulation and experimental test. The results show that when ultrasonic amplitude was 0.2-0.55 m, the forming quality of repaired layers was better; When ultrasonic amplitude was 0.4 m, the effect of ultrasonic on molten pool was mainly about mechanical effect and thermal effect, not ultrasonic cavitation effect. The mechanical effect declines the porosity rate of organization, but the mechanical force was less than the epitaxial growth driving force of crystalline grain in repaired layers so that the growth of -columnar grain along the direction of deposition could not be blocked; The mechanical effect breaks the -lath of lamellar microstructure and the thermal effect makes the solidification speed slow, as a result, the -lath was becoming short and thick.