Many new materials with narrow band gap are studied which are active photocatalysts under visible light irradiation. Anion doping of transition metal oxides such as TiO2-xNx [11], TaON could decrease the band gap [13-16]. Nitrides like Ta3N5 [13-15] are also visible light photocatalyst but most of them are unstable under irradiation. The hybridization of primal orbitals in multi metals oxides due to the orbitals of transition elements results in narrowing the band gap. As Zou et al., found that InNbO4 and InTaO4 split water into H and O2 under visible light irradiation [17-20]. The electronic structures of multi metals oxides such as AgInW2O8, [21] AgTaO3 ,[12] and AgNbO3,[22] show that their valence bands (VB) are formed by the hybridization of Ag-4d and O-2p states. While the conduction bands (CB) are formed by the hybridization of Ag-5s and other orbitals. Like In-5s state and W-5d state in AgW2O8. In the previous study the individual contribution of Ag to valence and conduction band has not been shown clearly. We have calculated the electronic structure which shows the individual contribution of Ag to the conduction and valence band. The AgAlO2 exists in two forms, hexagonal structure and orthorhombic structure. The later structure has dense polyhedron layers, which is considered to be more suitable for transferring electron-hole pairs [23]. Due to the structural advantage, orthorhombic crystal structure with space group Pna21 is used for the DFT calculations. AgAlO2 was synthesized and characterized by Li j and Sleight A.W. [24] and Ouyang et al. [23].