We prepared Li⁺ as a charge compensator using the high-temperature solid-state method and doped it into the silicate matrix of CaMgSiO₄∶Sm³⁺ to improve the luminescence properties of Sm³⁺ in CaMgSiO₄. The experimental results show that the CaMgSiO₄∶x Sm³⁺, y Li⁺ samples are pure phases, and introducing Sm³⁺and Li⁺ do not change the crystal structure. Under the excitation of the near-ultraviolet of 400 nm caused by the 4f-4f transition of Sm³⁺ ions, the emission peaks of CaMgSiO₄∶Sm³⁺ are 562, 576, 601, and 650 nm respectively. Additionally, from the spectra of co-doped samples, incorporating Li⁺ significantly enhances the luminescence intensity and emission peak integral area of Sm³⁺. Moreover, the color coordinates of the samples are in the red region (0.605, 0.394) and the color purity is up to 93.3%. At 150 °C, the peak intensity remains at 73.5% of that at room temperature, indicating that the phosphor has good thermal stability. The phosphor has a potential application prospect in solid lighting.