There is great influence on the output electro-optical convention efficiency for the different gas pressure and different gas mixture ratio in high power pulsed TEA CO2 laser. Therefore the output energy of laser changes with various gas pressures or various gas ratios in the laser resonator, which the convention efficiency of laser also increases accordingly. The experimental results show that the best value exists for laser output electro-optical convention efficiency when the gas ratio of CO2:N2:He equals 3:9:28. Under the condition of same injection exciting electric energy and total gas pressure 40kPa, the output energy can achieve 24.6J when single pulse discharges; the laser electro-optical convention efficiency can achieve 16.4% when laser works at high repetition rate and continuous discharge. Laser can operate continuously and steadily at maximum 500Hz.