A charcoal film preparing method is disclosed. Film formation of charcoal effectively overcomes loss and cyclic use issues in a using process of charcoal particles. The method is a novel method for applying charcoal to devices. The charcoal film exists stably, is independent of a substrate and has good mechanical strength. The film has adsorption and particle interception capabilities, and has high pollution resistance and regeneration cyclic use capabilities. According to the properties, the multifunctional film can achieve effective removal of organic matter pollutants in a dissolved state and effective interception of particle pollutants, can be recycled, and can be applied for treatment of polluted water bodies in the environment, air cleaning, drinking water purification, soil pollution restoration, and other fields.