<p>As a kind of difficult-to-machine material, the poor machinability of Ti6Al4V seriously limits its wide application. The laser-ultrasonic-vibration assisted machining (LUVM), as a new composite processing method, has shown great potential in improving the machinability of Ti6Al4V. In order to study the effect of processing parameters of LUVM on the cutting performance of Ti6Al4V, a finite element method (FEM) model of LUVM was established by applying surface heat flux and ultrasonic vibration load to the FEM model of conventional turning (CT). A kind of flat-top laser spot was proposed for the LUVM, which can provide a better preheating effect on the area of workpiece to be cut. The cutting performance was mainly explored from two aspects of cutting force and tool temperature based on numerical analysis. The results show that the tool-workpiece contact ratio (TWCR) caused by the ultrasonic vibration and the preheating temperature in cutting area are the key factors to influence the cutting performance of LUVM. The increase of amplitude and frequency can reduce the TWCR, resulting in a reduction in cutting force and tool temperature. The increase in cutting speed, feed rate and preheating distance can reduce the preheating temperature in cutting area, and the cutting force of LUVM increases accordingly. On the contrary, the increase in laser power can enhance the preheating effect to reduce the cutting force and increase the tool temperature. The results also further indicate that if one processing parameter of LUVM changes, the other processing parameters can also need to be considered for appropriate adjustment to achieve better cutting performance of Ti6Al4V.</p>