The invention provides a method for extracting fluorescent carbon quantum dots from semi coke. The method comprises the following steps: firstly, adding semi coke powder into a 4M to 6M nitric acid solution, and carrying out stirred refluxing at the temperature of 80 DEG C to 120 DEG C; carrying out natural cooling, then, carrying out centrifugation for 30 minutes to 60 minutes at the rate of 10,000r/min to 15,000r/min, collecting supernatant, removing precipitates, and drying the obtained supernatant by distillation in a reduced-pressure distillation manner, so as to obtain black solids; dispersing the black solids in deionized water, carrying out neutralizing by ammonia water, then, carrying out centrifugation for 30 minutes to 60 minutes at the rate of 10,000r/min, and collecting supernatant; dialyzing the supernatant by dialysis bags, collecting solutions in the dialysis bags, and carrying out vacuum drying for 24 hours to 48 hours at the temperature of 60 DEG C to 80 DEG C, thereby obtaining the carbon quantum dots. According to the method, the semi coke which is low in cost and easy in raw material obtaining is adopted as a carbon source, and the carbon quantum dots can be obtained through simple chemical oxidation, evaporation, neutralization, centrifugation and dialysis treatment processes. The carbon quantum dots have the particle size of 3nm to 5nm and are uniform in dispersion, and surfaces of the carbon quantum dots have a large number of carboxyl groups and hydroxyl groups, so that a relatively good fluorescent property is shown.