The compound Ca₂GdSbO₆ with a stable double perovskite structure is one of the high-quality materials used as a phosphor matrix. A new series of reddish-orange phosphors Ca₂Gd_{1 - x} SbO₆:xSm³⁺ (x = 0、0.01、0.02、0.03、0.04、0.05、0.06)were synthesized by high-temperature solid-state method. The phase composition, optical properties, crystal structure and chemical purity of the prepared phosphors were characterized via X-ray diffractometer (XRD), scanning electron microscope (SEM), photoluminescence spectroscope (PL), high-temperature fluorescence spectroscope and fluorescence decay lifetime measurement. The incorporation of Sm may endow the synthesized phosphor Ca₂Gd_{1 - x} SbO₆:xSm³⁺ with ions Sm³⁺ as its luminescent centers with the peculiar ⁴G_5/2→⁶H_7/2 transition of Sm³⁺ at 597 nm, so that the synthesized phosphor may emit the orange-red light at 597 nm under the excitation of the light at 407 nm. As the concentration of Sm³⁺ ions increase, the luminous intensity of Ca₂GdSbO₆:Sm³⁺ phosphors increases first, and then decreases. According to Dexter's theory, the concentration quenching is dominated by the electric dipole-dipole interaction, and the optimum doping of Sm³⁺ ions is concentration x = 0.03. The test shows that the color purity of the best-doped sample is about 99.3%, and the color coordinates are (0.6146, 0.3826). The thermal stability was further studied, and it was found that the emission intensity was only attenuated by 5.56% at 453 K. The above results show that the new red-orange light-emitting Ca₂GdSbO₆:Sm³⁺ phosphor is promising to be applied in the field of white LED.