The invention discloses a preparation method for water-soluble multicolor carbon quantum points by microwave radiation. A precursor solution is prepared by uniformly mixing an organic carbon source and ultrapure water, and is put into a glass tube specialized for microwave radiation, and microwave radiation is performed in a microwave reactor to prepare the water-soluble multicolor carbon quantum points. The method is performed completely in a water phase, and the method has safe operation, speediness, convenience, small toxicity and easily available and safe raw materials. The water-soluble multicolor carbon quantum points have good monodispersity, good fluorescence property, high quantum yield, good stability and good water solubility. The water-soluble multicolor carbon quantum points can be used for biological detection and analyses as fluorescence indicators.