Characteristics of combustion and radiation of a gas burner were examined in order to shift the fuel from a heavy oil and coal to a natural gas with the lowest C/H ratio and to reduce CO_2 emission from the burner of industrial furnaces and electric power plants. The energy flux radiated from the flame indicates a high value in the area of the high temperature and the high concentration of CO_2, CO. A high radiation intensity appears in the radiative wavelength bands of CO_2, CO and H_2O. It means that characteristics of radiation from the gas flame can be controlled by changing characteristics of combustion in the gas burner.