Fine cracks are easy to occur in the processing of monocrystalline silicon, which affects the surface processing quality. Laser assisted machining (LAM) can soften the substitute machining area, effectively reduce the cutting force, extend the tool life and improve the surface quality. In this paper, a thermo mechanical coupled smooth particle model is established to simulate the laser assisted turning process of single crystal silicon. Under different temperature conditions, crack propagation damage and cutting stress are explored; The influence of speed and cutting depth on surface roughness. Finally, the accuracy of simulation results is verified by laser assisted cutting experiments. The results show that increasing the temperature is beneficial to the plastic cutting of monocrystalline silicon. With the increase of the cutting zone temperature, the tool stress gradually decreases. The tool stress at 300 ℃ is about 50% lower than that at room temperature, and the surface processing quality is significantly improved. At 600 ℃, the chip is a plastic flow sawtooth line, and the plasticity is greatly improved. During cutting, a smaller cutting depth shall be selected, the rotating speed shall be lower than 4500r/min, and the surface roughness Sa of monocrystalline silicon can be less than 1nm.