The feed water enters to the boiler drum after being heated in the three groups of economizer horizontally arranged. The boiler water in boiler drum enters the water-cooling lower header, riser, water-cooling panel, upper header via the centralized down comer and distribution pipe, and then enters the boiler drum via the transfer pipe. The steam-water separation device is provided in the  boiler drum. The saturated steam is introduced to the steam-cooled cyclone separator from the steam connecting pipe on the top of the boiler drum and via the connecting flue, and then it passes through the tail steam-cooled enclosure wall tube, low temperature superheater, stage-1 water -spraying attemperator,  the platen superheater inside the boiler, stage-2 water -spraying attemperator and high temperature superheater in turn, at last the qualified superheated steam is introduced to the steam turbine or temperature and pressure reducer.