The invention relates to a preparation method of super-high-quantum-yield carbon quantum dots with citric acid-urea as raw materials. The preparation method includes the steps that citric acid and urea serve as the raw materials for a hydrothermal reaction, a hydrothermal product is obtained and dried, pyrolysis calcination is conducted, and a calcined product is obtained; the calcined product is ground and filtered, and then the super-high-quantum-yield carbon quantum dots are obtained. The preparation method is mild in reaction condition and easy and convenient to operate, and the raw materials are easy to obtain, cheap and environmentally friendly. The prepared carbon quantum dots are high in quantum efficiency, good in monodispersity, stable in luminescent performance, free of twinkling phenomena, good in biocompatibility and the like.