A series of studies were conducted for surface valency in blue tungsten oxides by using pho-toemission technique. Rusults show that, the blue tungsten oxide contains not only one kind of valency, but conbination of two valences, namely the conbination of W+5 and W+6, and also the process of argon ion eching and high temperature treatment all induce the loss of oxygen in W-chemical reduction process, which causes W transfer from high valence to low valence. Meanwhile, the density of state near Fermi level increases with the change from high valence to low valence.