This work aims to develop a physically based numerical model to calculate the valence electron structures and atomic bonding of the precipitates of Al-Cu-Mg-Ag alloy with high Cu/Mg ratio with the empirical electron theory of solids and molecules. The valence electron structures and the interface conjunction of W phase were calculated, and they were investigated with the phase structure factor. Accordingly, on the basis of the empirical electron theory of solid and molecules, the precipitation and stability of the precipitates and the strengthening mechanism of Al-Cu-Mg-Ag alloy were explained on the level of valence electron structure