To determine the optimal doping concentration, a series of Mn:MgAl2O4 were successfully prepared through vacuum-sintering with the highest doping concentration up to 35%. Samples with a low doping concentration exhibit a light green color. When the doping concentration increases, its color becomes deeper and deeper and when the doping concentration reaches 14%, their colors become brown and deeper brown when their concentrations further increase. The crystal phases of the samples were manifested by XRD measurements and their photoluminescence properties were studied. Combined with phase analysis, optimal doping concentration of transparent ceramics has been determined. In addition, the mechanism for fluorescence of Mn:MgAl2O4 transparent ceramics has also been discussed.