The optical‐magnetic multifunctional materials are of great importance owing to their potential applications in intersect discipline fields. However, the multifunctional materials with satisfied optical and magnetic property are limited, and the modulation mechanism of their magneto‐optical property related to their structure feature is ambiguous. Here, a new multifunctional solid solution phosphors Ca18K3Sc1‐xSmx(PO4)14 (0 ≤ x ≤ 1) are designed based on composition engineering and are successfully synthesized. The detailed structure feature including the structural evolution of the crystallographic parameters and local lattice environment as well as polyhedral distortion behavior are investigated through X‐ray diffraction Rietveld structure refinement for Ca18K3Sc1‐xSmx(PO4)14 in the full range (0 ≤ x ≤ 1). The photoluminescence spectra indicate that Ca18K3Sc1‐xSmx(PO4)14 (0 ≤ x ≤ 1) can emit intense orange‐red emission (IQE~42.6%) under ultraviolet light excitation ascribed to the4G5/2 ‐6H7/2 transition of Sm3+ ions. The structure modulated luminescence behavior, for example, the tunable emission ratio of I648/I565, high quenching content, and electric multipole interaction mechanism are studied. The versatile phosphors can exhibit tunable orange‐red cathodoluminescence emission along with increasing the accelerating voltage. The electron transition mechanism of the photoluminescence and cathodoluminescence behavior is further discussed through a simple schematic diagram. Moreover, Ca18K3Sc1‐xSmx(PO4)14 (0 ≤ x ≤ 1) shows a ferromagnetic behavior with controllable magnetization and coercive field. Finally, the impact of Fe ions on the photoluminescence and magnetic property of Ca18K3Sc1‐yFey(PO4)14: 0.4Sm3+ (0 ≤ y ≤ 0.05 and y = 1) phosphors are investigated. The current research can provide some ideas and mechanism to design and investigate more novel magneto‐optical muntifunctional materials for versatile applications in intersect disciplines.