Based on the operation data of a 350 MW generator unit and the calculation of variable working conditions of its condenser, the influences of the unit load, circulating water flow and circulating water temperature on the condenser backpressure was analyzed qualitatively and quantitatively by the control variable method. Furthermore, the influences of these parameters on the heat rate of the unit, the net power of the unit and the coal consumption rate of the whole plant were studied. Considering the net output of the unit as an object function, the optimal backpressure and optimal circulating water flow were presented. The optimal adjustment scheme of the unit under normal load (75%) and the comparison of coal consumption rates before and after adjustment were given. By optimization, the switching point for the single pump turned to double pumps operation was adjusted from 16℃ to 18℃. By adjusting the running mode of circulating water pump, the average coal consumption can be saved by about 0.25 g/(kW·h).