Abstract: The fast flow axial CO2 laser is usually used for laser cutting because of its good laser beam quality.To ensure the stability of the output laser power,the working gas should be stabilized at an optimal pressure.Based on exact study on the working theory and effect factors,PID with intelligent integral separation is applied to adjust the pressure of the working gas.The gas pressure control precision is improved with this simple and practical algorithm.Finally,the precision and stability of the output laser power can be ensured.All the above are testified by experiments.