Based on thermodynamic principles, the coupled systems performance of the Rankine cycle and the transcritical CO2 compression cycles with a throttle valve and the cycle with an expander were analyzed, respectively. The results show that the corresponding maximum performance in transcritical CO2 heat pump, there is an optimal efficiency of the coupled system. With the temperature increasing of boiler feed water, the efficiency of the two coupled system showed an increasing trend; with increasing of discharge pressure of condenser or outlet temperature of gas cooler, both of the two kinds coupled system efficiency showed a downward trend. Under the same conditions, the efficiency of the coupled system with an expander is better than the system with a throttle valve. This paper can provide the fundamental datum for the power plant waste heat recovery.