SrSnO3 phosphor powders were synthesized with two different contents of activator ions Eu3+ and Tb3+ using thesolid-state reaction method. The structural, morphological, and optical properties of the phosphors were investigated using X-ray diffractometry, field-emission scanning electron microscopy, and fluorescence spectrophotometry, respectively. All thephosphors showed a cubic structure, irrespective of the type and the content ratio of activator ions. For Eu3+-doped SrSnO3phosphors, the intensity of the 620nm red emission spectrum resulting from the 5D0→7F2 transition of Eu3+ was stronger thanthat of the 595nm orange emission signal due to the 5D0→7F1 transition in the range 0.01-0.05mol of Eu3+, but the ratio ofthe intensity was reversed in the range 0.10-0.20mol of Eu3+. The variation in the emission intensity indicates that the sitesymmetry of the Eu3+ ions around the host crystal was changed from non-inversion symmetry to inversion. For the Tb3+-dopedSrSnO3 phosphors under excitation at 281nm, one strong green emission band at 550nm and several weak bands wereobserved. These results suggest that the optimum red and green emission signals can be realized when the activator ion contentfor Eu3+- or Tb3+-doped SrSnO3 phosphors is 0.20mol and 0.15mol, respectively.