By measuring the discontinuous oscillation components of the continuous frequency spectrum for the beam noise of He-Cd lasers, it has been discovered that the boundary conditions of the laser tube, the discharge current and Cd atom density have influences on the frequency and the power output of the characteristic peak of the ionization wave frequency, the de’pth of modulation, the 1/f noise bandwidth and other noise amplitudes. A 100% depth of modulation at that characteristic peak has been obtained.