The gas generator cycle and staged combustion cycle with LO₂/RP-1 propellants combination have been analyzed in this paper. The maximum combustion chamber pressure for various cycles has been found. The effect of combustion chamber pressure，sea level thrust，chamber mixture ratio，nozzle exit diameter on engine specific impulse and system balance parameters is given. The sensitivity dependences of effeciences，turbine pressure ratio，gas generator (or preburner) mixture ratio and other design parameters on balance parameters have been investigated