Abstract: Dynamic characteristics of power plant condenser were studied using small disturbance theory and thermo-economic state equations, during which the influence of water atomization make-up mode on both the condenser vacuum and unit efficiency was analyzed, while the variation law of unit efficiency with water make-up mode and make-up water temperature studied with actual examples. Results show that when chemical water of a certain temperature is atomized by nozzle and fed into the system through condenser throat, the cold end loss of system may be reduced, the back pressure of unit may be lowered and the thermal economy of system may be raised; with the rise of make-up water temperature, ΔP reduces gradually while ΔN rises slowly.