A new type of CO₂laser tube has been designed by using a plasma tube having rectangular discharge cross-section and is excited by both the axial glow discharge and the transverse silent discharge. In this paper, the principle of design is described and the transverse distribution of electron concentration in the laser tube is discussed theoretically. Furthermore, its working characteristics are studied experimentally and compared with those excited by the only DC glow discharge. Under the action of transverse silent discharge, the laser power, the gas-filled pressure and the fraction of N₂in the laser are increased obviously, the laser efficiency is increased, too. Both the laser power and efficiency can be simultaneously optimized by choicing the discharge current.