The enhancement of photoluminescence (PL) stability of colloidal quantum dots (CQDs) is of great significance in light-emitting devices. In this work, the PL stability of CdTe CQDs under time storage, strong light irradiation, acid and alkali corrosion and low temperature freezing is analyzed, and the PL quenching mechanism in a harsh environment is analyzed. Furthermore, the PL stability is extremely improved by core-shell coating, film deposition and polymer encapsulation. This solves the problem of rapid dropping of the PL intensity at the initial illumination stage and improves the corrosion resistance in an acidic environment and long-term storage stability of film devices. CQD polymer films have an interesting phenomenon of fluorescence enhancement under illumination due to the light-soaking effect. Biocompatible coating and encapsulation materials expand the application of CQD devices in the field of biological tissue imaging and sensing. Through the PL regulation of CQD solutions and the simple superposition of self-supporting films, a panchromatic light-emitting device with broadband adjustable chromaticity is realized. The solid-state stable whispering-gallery-mode (WGM) laser is realized by monodisperse SiO2 microspheres embedded in the film. This work is of great significance for the application of CQDs in flexible light-emitting devices.