Power plants with CO2 utilization have been designed by Allam, Mateant, Turbocon, etc. One of the main problems of this plant is a condenser for steam-gas mixture with high concentration of non-condensable gas. The process of development of steam condenser for steam-gas mixture is described. Its design is based on the idea of maintaining a constant steam-gas mixture velocity along the steam condensation channel. The shape of the channel with constant SGM velocity is described. To research the heat-mass transfer of gas-team mixture the test plant with tubes crosscut by thermocouples is realized. In the process of testing, gas-steam mixture velocity, pressure and air concentration changed from 0% to 18%. The experimental results have been summarized in a dimensionless equation. The pressure drop and increase of air concentration contribute to the decrease of saturation temperature. The optimal velocity is reached when the surface area of the channel in the condenser is minimal. The optimal velocity is about 30 – 50 m/s. The research results are implemented in the experimental model of high-efficiency condenser. The heat transfer coefficient in this model is equal to about 4500 – 2700 W/(m2K) if air concentration at the inlet is 0–8 %. The designs of high-efficiency condenser for gas-steam turbine plant of 25 MW capacity and the condenser with vertical tubes have been presented.