Magnesium-doped zinc oxide phosphors with the formula of MgxZn1−xO were synthesized by sol–gel method, and the crystal structure and luminescent properties were investigated by means of XRD, SEM, FTIR, Raman spectrum, EPR, DRS and PL. The results indicated that the materials consisting of MgxZn1−xO particles exhibit good crystallinity and the particle size varies with the calcining temperature. An obvious blue shift of excitation band was observed in samples as the doping concentration was increased from 5 at% to 10 at%. The optimal concentration for obtaining the highest photoluminescent intensity for MgxZn1−xO phosphors was 10 at% (calcined at 875 °C for 3 h). Raman and EPR results suggested that the red emission of Mg-doped ZnO phosphors was attributed to zinc vacancies and oxygen vacancies.