Laser drilling uses gas as circulating medium to clean holes， and the reasonable gas flow properties are the guarantee for hole cleaning efficiency. Gas nozzle is the direct factor affecting gas flow properties， and its unreasonable structural design seriously affects the efficiency of laser drilling. Aiming at the gas nozzle in the laser drilling experimental platform， the basic type of the nozzle is constructed， the nozzle structure size that affects the gas hole cleaning efficiency is analyzed， and the simulation scheme is formulated. Moreover， the gas flow field is simulated by Fluent， and the hole cleaning effect is analyzed. The nozzle structure and simulation results are analyzed by neural network， and the neural network model is trained to get and verify the best nozzle structure parameters for hole cleaning efficiency， which provides reference for the nozzle structure design.