The green-emitting (Ce,Tb)MgAl11O19 (CTMA) phosphor was prepared by the conventional high temperature solid-state reaction method. The effect of fluxes on the crystal structure, particle morphology, size distribution and photoluminescence properties of CTMA phosphor was investigated by means of the X-ray powder diffraction, scanning electron microscopy and photoluminescence spectrum. The results showed that the addition of appropriate amount of MgF2-H3BO3 flux improved the phase purity of CTMA phosphor, and influenced the growth of different crystal plane; furthermore, the particle morphology of CTMA phosphor became regular and size distribution narrowed. In addition, the CTMA phosphor prepared with MgF2-H3BO3 flux displayed higher photoluminescence intensity than that of the phosphor prepared with MgF2, H3BO3 or without flux. As a result, the optimum content of fluxes was 0.10 mol/mol MgF2 and 0.04 mol/mol H3BO3, and the maximum photoluminescence intensity of the CTMA phosphor prepared with MgF2-H3BO3 flux was 167% of that of the phosphor prepared without flux.