$ZnGa_2O_4$ powder were prepared by combustion method and $Mn^{2+}$ ions, a green luminescence activator, and $Cr^{3+}$ ions, a red luminescence activator were separately doped into $ZnGa_2O_4$. The characteristics of the synthesized nano powder were investigated by means of X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and photoluminescence (PL). The various $ZnGa_2O_4$ peaks, with the (311) main peak, appeared at all sintering temperature XRD patterns. The PL specctrums of $ZnGa_2O_4$ powder showed main peak of 425 nm, and maximum intensity at the sintering temperature of $1200^{circ}C$. SEM images shown that nano sized particles(about 200 nm) were of spherical shape. The characteristics of $ZnGa_2O_4$ containing 0.004 mol $Mn^{2+}$(505 nm, green) and $ZnGa_2O_4$ containg 0.002 mol $Cr^{3+}$ (696 nm, red) were shown to be the best.