By using inorganic salts as raw materials and citric acid as complexing agent, spinel oxide ZnGa 2 O 4 and Mn 2 + , Eu 3 + -doped ZnGa 2 O 4 phosphor powders were prepared by a citrate-gel process. X-ray diffraction (XRD), TG-DTA, FT-IR and luminescence excitation and emission spectra were used to characterize the resulting products. The results of XRD reveal that the powders begin to crystallize at 500 o C and pure ZnGa 2 O 4 phase is obtained at 700 o C, which agrees well with the results of TG-DTA and FT-IR. In the crystalline ZnGa 2 O 4 , the Eu 3 + shows its characteristic red (615 nm, 5 D 0 - 7 F 2 ) emission with a quenching concentration of 5 mol% (of Ga 3 + ), and the Mn 2 + shows green emission (505 nm, 4 T 1 - 6 A 1 ) with a quenching concentration of 0.1 mol% (of Zn 2 + ). The luminescence mechanism of ZnGa 2 O 4 :Mn 2 + /Eu 3 + is presented.