Steam temperature has been raised to 604/602°C at the Chugoku Electric Power Co., Inc., Misumi Thermal Power Station No.1 coal-fired, supercritical sliding pressure operation boiler supplied by MHI with a vertical furnace waterwall. The boiler achieved high efficiency and low NO_X emission with A-PM burner and MRSⅡ pulverizer. This paper reports the boiler's design features and operation results, e. g., (1) the highly reliable vertical furnace waterwall, which uses rifled tubing, (2) low NO_X and low unburned carbon in fly ash owing to the A-PM burner and MRSⅡ pulverizer, and (3) the higher boiler efficiency of 91.8％ and flexible boiler operation in coal exclusive firing at enough lower load than guaranteed minimum load of 30％(15％ load was confirmed in trial operation).