Many research efforts have focused on designing new inorganic phosphors to meet different application requirements. The structure-photoluminescence relationship between activator ions and the matrix lattice plays an irreparable role in designing target phosphors. Herein, a series of ABP2O7:Mn2+ (A = Ba/Sr; B = Mg/Zn) phosphors are prepared for a detailed study on the relationship between the luminescence performance and spatial structure and symmetry of the doping site of Mn2+. Due to the weak interaction between nearest B-B pairs, [BO5] is defined as an isolated coordination polyhedron whose structure and symmetry directly influence the photoluminescence of Mn2+. The emission wavelength of Mn2+ is ∼620 nm when it occupies the triangular bipyramid [MgO5] in BaMgP2O7. When Mn2+ occupies the quadrangular pyramid-typed [MgO5] or [ZnO5] in SrMgP2O7, SrZnP2O7, and BaZnP2O7, the emission wavelengths peak at ∼670 nm. We propose a conception of isolated coordination polyhedral confinement to clarify the luminescence performance of Mn2+ in the fivefold coordination configuration with different geometries, which has great theoretical research significance for designing inorganic phosphors.