The invention belongs to the technical field of molecular probes, in particular to a luminescent carbon quantum dot, a preparation method and application thereof, and a method for detecting arginine in an aqueous solution by using the luminescent carbon quantum dot, in particular to a method for synthesizing the carbon quantum dot by using 2-methoxy-4-methylphenol and o-phenylenediamine as raw materials by a hydrothermal synthesis method and detecting arginine by fluorescence. The synthesis cost of the carbon quantum dot is low, the method is simple, the synthesized carbon quantum dot does notcontain heavy metals, and has low toxicity, and the carbon quantum dot provided by the invention is completely water-soluble, and can detect arginine in water, the detection limit is 78.11 mu M, thefluorescence quantum yield in water is 6.3%, and the luminescent carbon quantum dot has very good light stability, anti-interference and relatively good application prospects.