The traditional commercial white LED has low color rendering index due to the lack of red light component. In order to improve the color rendering performance of white LED, Sm3+ can be added to the fluorescent powder to enhance the emission ability of orange and red light. Double perovskite oxide Ca2YNbO6：Sm3+ phosphors with red luminescence are prepared by traditional high temperature solid phase method. The crystal structure, elemental composition, emission spectrum, photoluminescence spectrum, thermal stability and fluorescence lifetime of the fluorescent powder are studied in detail. Results show that the phosphor is a pure compound with particle size about 5 μm, Sm3+ has a strong red emission at 650 nm when excited at 408 nm. According to data fitting, it is shown that the luminescence of phosphor belongs to Sm3+ electric dipole-dipole interaction process. High temperature testing shows that the oxide fluorescent powder has high thermal stability. By mixing commercial blue and green powder with Ca2Y0.96NbO6：0.04Sm3+ powder and excited by 365 nm-InGaN chip, a warm white LED with color coordinate of (0.344, 0.350), color temperature of 4 989 K and a color rendering index of 81 is realized.