The invention discloses a method for preparing a 
photoluminescence carbon 
quantum dot. The method includes the following steps of 
drying and dehydrating a 
solid residue obtained after squeezing soybeans into soya-bean milk, placing the dried and dehydrated 
solid residue in an electrothermal blowing 
dry box to heat and carbonize to obtain a crude product of the carbon 
quantum dot, 
grinding the crude product of the carbon 
quantum dot, sieving, dispersing the sieved crude product of the carbon 
quantum dot in deionized water, uniformly stirring, still standing, centrifuging, evaporating an obtained 
aqueous solution containing the carbon 
quantum dot, and 
freeze drying to form a powdered shape to finally obtain the 
photoluminescence carbon 
quantum dot. According to the method for preparing the 
photoluminescence carbon quantum dot, a household bean juice maker is used for obtaining soybean dregs which serve as raw materials, the source of the raw materials is wide, the photoluminescence carbon quantum dot is prepared through low temperature heating and 
carbonization, the operation is simple, the cost is low, the yield is high, the preparation 
process equipment is simple and easy, the operation can be completed within an extremely short time, and the method is easy to popularize.