To simplify the structure of the polarized CO₂ waveguide laser and its manufacture technology,a type of the polarized CO₂2 waveguide laser with new polarization device was presented. This new polarization device is a rectangular waveguide cathode in fact. By utilizing the special action of the device at the mouth of discharge waveguide to the light beam in the resonator,only the light beam with the polarization of electric field in one direction can oscillate,and the polarized light can be exported steadily. The polarizing mechanism of the laser was analyzed theoretically,and the linear polarization degree of the output light was measured experimentally. The new laser,with over 98% linear polarization degree of output light,has characteristics of simple structure,low price,and so on.