The invention discloses a charcoal amine sulfur dual-group modification method. The method comprises the following steps that charcoal is subjected to nitric acid acidification oxidation, after ultrasonic concussion is performed for 2-5 h, centrifugal washing is performed till the charcoal is neutral to obtain oxidized activated charcoal BC-O; on the basis of the oxidized activated charcoal BC-O, the proper PH is adjusted, methanal is added under the constant temperature of 40-60 DEG C, ta reaction is performed to 20-50 min, polyamine substances are added dropwise, a reaction is performed for 4-6 h, and amino modified charcoal BC-N is obtained; cooling is performed to reach the room temperature, NaOH with the mass fraction being 40-50% is added, carbon disulfide is added dropwise to perform a sulfenyl reaction, after dropping is completed, the temperature is increased to 60-80 DEG C, and a reaction is performed for 5-7 h; centrifugal washing is performed, and after drying, the amine sulfur dual-group modified charcoal BC-SN is obtained. The prepared modified charcoal has the advantages that surface groups are abundant, the specific surface area is large, and the pore volume is large, and heavy metal ions are adsorbed and passivated.