Carbon quantum dots (CQDs) are a novel type of carbon material with unique properties such as adjustable particle size, light resistance, ease of functionalization, low toxicity, excellent biocompatibility, and high water solubility. They are widely used in various fields including optoelectronics, bioimaging, drug delivery, cancer therapy, sensors, and environmental remediation. This review summarizes the properties, preparation methods, raw materials, and heteroatom doping of CQDs, as well as their applications. The article discusses the challenges in the synthesis and application of CQDs and highlights the latest research progress. The preparation methods of CQDs include top-down methods such as arc discharge, laser ablation, electrochemical and chemical oxidation, and bottom-up methods such as templates, microwave, and hydrothermal techniques. The review also covers the separation and purification of CQDs, the materials used for their preparation, and the heteroatom doping of CQDs. The review emphasizes the importance of heteroatom doping in improving the properties of CQDs and their potential applications in various fields. The review provides a comprehensive overview of the current state of research on CQDs and their potential for future development.Carbon quantum dots (CQDs) are a novel type of carbon material with unique properties such as adjustable particle size, light resistance, ease of functionalization, low toxicity, excellent biocompatibility, and high water solubility. They are widely used in various fields including optoelectronics, bioimaging, drug delivery, cancer therapy, sensors, and environmental remediation. This review summarizes the properties, preparation methods, raw materials, and heteroatom doping of CQDs, as well as their applications. The article discusses the challenges in the synthesis and application of CQDs and highlights the latest research progress. The preparation methods of CQDs include top-down methods such as arc discharge, laser ablation, electrochemical and chemical oxidation, and bottom-up methods such as templates, microwave, and hydrothermal techniques. The review also covers the separation and purification of CQDs, the materials used for their preparation, and the heteroatom doping of CQDs. The review emphasizes the importance of heteroatom doping in improving the properties of CQDs and their potential applications in various fields. The review provides a comprehensive overview of the current state of research on CQDs and their potential for future development.