Abstract: Several parameters that affect the output pulse characteristics of electro-optically(E-O) cavity-dumped RF waveguide laser have been discussed.By changing the rising time of high voltage pulse in CdTe crystal and reflectivity of Brewster window,the varieties of output pulse width and peak power of cavity-dumped laser are theoretically studied.By changing these parameters,in a home-made CdTe E-O cavity-dumped double-channel RF excited CO2 waveguide laser,which might be used as a light sources in a heterodyne imaging lidar system,we have obtained the cavity dumped pulses width at FWHM from 20ns to 30ns.