The advantages and disadvantages of the steam distribution control strategy by combination valve and sequence valve for 600MW aircooled unit were introduced. The variations of the parameters, such as the bearing bush temperature, the locus of shaft center, the position of shaft center and others, of the unit before and after optimization of the valve acting sequence were analyzed. Combining with practical project, a solution was proposed, which can be used as reference for other power plants in optimization of steam distribution control strategy.