Beryllium bronze is widely used in electronic industry as stretchy component. The evaluation of treatment effect depends on experience at present. This article tries to detect the strengthen phase in Beryllium bronze quantitatively. The XRD is used applying external standard method in order to detect the amount of strengthen phase directly. And SEM and OM are used too for proper binary image. The results showed the pictures taken by OM under dark field model at specific parameter were suitable for computer to distinguish the strengthen phase from the base. This method could quantitatively detect the amount of the second phase successfully through making full use of dark field model of OM. At the same time, this method is of efficiency and economy.