Abstract: Taking a typical domestic gas and steam combined cycle unit as the research object, a five-level system for energy efficiency indicators was established. Based on the simulation calculation model by Thermoflow software, analyses were conducted on the characteristics of the unit under different conditions, and the reference values and heat consumption deviation factors of main energy efficiency indicators within full load conditions were calculated. After which, the effects of indicators on the unit economy were compared and analyzed. Calculation results show that the unit economy is significantly influenced by the main steam pressure, the turbine back pressure, and the compressor efficiency.