The invention relates to a detection technology of 
copper ions, and in particular relates to a preparation method of a reduced carbon 
quantum dot containing 
calcium alginate gel for detecting 
copper ions. The preparation method of the carbon 
quantum dot containing 
calcium alginate gel for detecting the 
copper ions comprises the following steps of: preparing fluorescent 
carbon quantum dots; neutralizing the fluorescent 
carbon quantum dots, adding 
sodium borohydride into the neutralized fluorescent 
carbon quantum dots to perform reduction; mixing deionized water with the neutralized fluorescent carbon 
quantum dots at equal volume, and adding 
sodium alginate into the mixture to obtain a 
sodium alginate 
sol; and spraying a 
calcium ion solution to the surface of the 
sol or soaking the 
sol into the calcium 
ion solution to perform crosslinking, and 
drying to obtain the 
calcium alginate gel. By using the characteristics that the carbon quantum dots have fluorescent characteristics, the 
fluorescence of the carbon quantum dots is enhanced after reduction, and the 
calcium alginate can enhance the fluorescent characteristics of the carbon quantum dots, when the copper ions are detected, the cost of an adopted fluorospectro 
photometer is low, the 
sample preparation and treatment steps are simple and easy to operate, and the detection sensitivity is high, so that the 
calcium alginate gel can be widely used for detecting the copper ions.