The No.1 and No.2 units in Yuncheng Power Generation Company are 600 MW air cooling units, the turbine efficiency of which had been far lower than the design value since operation. A series of measures of efficiency increase and consumption reduction were adopted to improve the units efficiency, such as the reformation of steam seal, the treatment of inner leakage in steam valve, the optimization of control valves characteristic curves and sliding pressure curves, the optimization of sequence valve control for high pressure control valve. After the implementation of these measures, the economy of the units has been greatly improved in low load condition, while the throttling loss of high pressure control valve has been obviously reduced in high load condition so that the efficiency of high pressure cylinder has been increased. According to the electricity generation of Yuncheng Power Generation Company in 2010, the economic benefits obtained from the treatment have exceeded 10 million yuan.