The structural style of the resonator of HGL-20 type CW CO2 laser is investigated The roles of the external-bridge-intracavity structure and optical cavity micro-ac^ust system for improving the stability of the laser resonator are discussed. The design characteristics of the electrical supply measuring system, the optical cavity and power measuring system, the vacuum measuring system, the auto gas filling-draining system, the temperature measuring system, the safety alarm system, etc., and the effect of these factors on the stability and the beam quality of the output laser are investigated.