Due to the simple preparation, low cost, and adjustable bandgap via changing their sizes in the near-infrared band, PbS colloidal quantum dots (QDs) have been widely used in many fields such as solar cell, infrared detection, LED, and biological imaging. However, instability limits further practical application. In this study, the instability mechanism of PbS colloidal QDs was investigated, and measures to improve their stability are discussed in terms of preparation, structure, preservation, and application. Measures and mechanisms for further improving stability are proposed, which have great value for their application and development.