Quantum dots are widely used in the field of luminescence because of their unique and excellent optical properties. The most prominent feature is that the spectral tuning is convenient, and only the size of the material needs to be changed to realize the tuning of the luminescence spectrum. In combination with the needs of practical applications, CdSe materials were selected as the main research object. By improving the process, introducing Schlenk line to isolate water and oxygen, using high temperature thermal injection method, adjusting the ratio of cadmium source and zinc source, selenium source and sulfur source in raw materials, the core-shell structure CdSe/ZnS red and green quantum dot materials with high color purity and high efficiency and stability were obtained. The synthetic quantum dots have a size of about 6.0 and 4.2 nm, luminescence peaks of 625 nm and 525 nm, the full width at half maximum (FWHM) in PL spectra of 30 and 28 nm, and photoluminescence quantum yield (PLQY) of 82% and 61%, respectively. And then the application of quantum dot LED in backlight display was studied. The composite red and green quantum dot materials were used to replace the phosphor materials in the traditional process. By improving the packaging method, the quantum dot light conversion layer was protected by a double-layer epoxy resin AB glue, at the same time, a PMMA lens coating was introduced to fundamentally isolate water and oxygen. Finally, the packed quantum dot white light-emitting diodes(wLEDs) have red, green and blue emission peaks of 630, 535 and 453 nm, respectively. The FWHM of PL spectra are 20, 28 and 30 nm. The three-segment spectral emission peaks have good symmetry on both sides, effectively solving the problem that the LED is missing in the red spectral band of the traditional phosphorwLEDs. And it achieves the advantages of good monochromaticity, high color purity, and high color saturation. The quantum dot wLEDs with CIE color coordinate (0.329, 0.324) was obtained under the condition of 20 mA current in the LED integrating sphere photochromic test system. The color coordinate was very closed to the standard white light. Its color temperature was 5 094 K, the luminous efficiency reached 94.72 lm·w-1, and the color rendering index Ra could approach 78.6, and the lifetime was more than 400 h. Finally, the quantum dot LED strip was packaged to complete the backlight. According to the quantum dot wLEDs emission spectrum gained from the test, we could obtain the sRGB color triangle, ie the color gamut. By comparing the NTSC1931 standard color gamut, we discovered a high color gamut quantum dot LED backlight with a colorgamut coverage of 109.7%. The LED backlight developed was made up of 240 quantum dot wLEDs and successfully demonstrated the 29-inch LCD TV panel for the first time. This result will further develop tailor-made quantum dots, especially in high-performance display applications.