In this paper,the velocity field and pressure field numerical simulation of the special cutting nozzle are carried out by Mixture model,the flow state of gas-liquid two phase flow in cutting nozzle is analyzed,and the change of velocity and pressure at different positions are analyzed.To study the effect of oxygen flow at different pressures on the speed change of ethanol fuel and the effect of oxygen flow under certain pressure on the atomization of ethanol gasoline at different speeds.By analyzing the underexpansion of static pressure on both sides of the fluid,it is concluded that the under-expansion jet is conducive to the mixing of air and liquid fuel.The simulation results show that increasing the speed difference of gas-liquid mixture can improve the atomization degree of ethanolgasoline at the outlet of the nozzle,which is beneficial to the full combustion.