It is found that there exists a notable axial pressure difference of 1 to 2 torr during the operation of the He-Cd laser, which is about a half of the He operation pressure or 3 times of the pressure difference in pure He electric discharge. The effects of pressure difference on laser output, noise and stability are investigated. After using a diffusion return path, the laser output power at 4416 A. is increased from 80mW to 110 ml, the noise is decreased to 1.3% at 44161 and to 0.9% at 3250A, and the stability of laser output is greatly improved. The rate of Langmuir flow moving along the direction from the cathode to the anode is calculated to be I5cm3/sec. The experiment results are discussed. The decrease of pressure difference may reduce the sputtering of cathode, and thus prolongs the lifetime of laser.