Hollow and dense BaMgAl₁₀O₁₇:Eu²⁺ (BAM) phosphor particles were synthesized by a spray pyrolysis process and their luminescent properties were investigated under vacuum ultraviolet (VUV) excitation as varying the increased with increasing the particle size. The dependence of the luminscent intensity on the particle size was greatly influenced by the morphology of BAM particles. For the BAM particles with a hollow structure, the luminescent intensity linearly increased with increasing the particle size. However, no significant change in the luminescent intensity was observed for dense particles as the particle size changed. Also, all dense BAM particles had higher photoluminescence intensity than that of the hollow ones regardless of the particle size. The luminescent intensity of BAM phosphor particles prepared by spray pyrolysis was found to have a linear relationship with the crystallite size. Therefore, it was concluded that suppressing the formation of a hollow structure and increasing the crystallite size are needed to obtain high luminous BAM phosphor particles with a spherical shape and fine size of less than 1 μm. On the basis of penetration depth of VUV, a simple relation equation between the particle size and the luminescent intensity was derived and correlated with experimental results in order to interpret the luminescent behavior of BAM phosphor as the particle size changes.