The invention discloses antibacterial soap and a preparation method thereof, and relates to the technical field of daily supplies. According to the antibacterial soap, lignosulfonate with surface activity, dispersion and adsorption characteristics, chelate properties, hard water resistance and synergetic inactivating action is added into a soap system, so that the soap system has good decontaminating and sterilizing functions under the condition of high-hardness water quality. The preparation method of the antibacterial soap has the advantages that the method is simple, low in production costand applicable to large-scale production and wide popularization. Moreover, the prepared antibacterial soap is free from any preservatives and other chemical substances, poisonless and harmless and has the advantages of strong detergency, good antibacterial effect, moisturizing and skin protection properties and the like.