应用阶面层理论和小扰动稳定性理论提出并分析激光切割前沿熔融层控制方程，认为熔融层流动趋于稳定的条件是由切应力驱动流动而非压力驱动流动或压力驱动流动为流动的次要因素，拉伐尔喷嘴出流特点正是流体速度高而压力较低，结合激光对喷嘴的特殊要求，提出了激光切割用拉伐尔喷嘴的设计依据和设计步骤，以及保证喷嘴正常工作所需的操作参数选取范围。 Based on the application of plane theory and small perturbation stability theory, the governing equation of molten layer in front of laser cutting is proposed and analyzed. It is considered that the condition that the flow in melt layer tends to be stable is that the shear stress-driven flow, not pressure-driven flow or pressure-driven flow Factors, Laval nozzle outflow characteristics is the fluid speed is high and the pressure is low, combined with the special requirements of the laser nozzle, laser cutting Laval nozzle design basis and design steps, and to ensure the normal nozzle Required operating parameters selection range.