The invention provides a method for preparing dibenzoyl peroxide by utilizing recycled mother liquor, and belongs to the field of preparation of organic peroxides. The method comprises the following steps: mixing a sodium hydroxide solution, hydrogen peroxide and surfactant recycled mother liquor to obtain reaction liquid, wherein the recycled mother liquor is the mother liquor formed through separation during the preparation of the dibenzoyl peroxide by taking sodium hydroxide, hydrogen peroxide and benzoyl chloride as raw materials; dropwise adding benzoyl chloride into the reaction liquid,and performing peroxidatic reaction to obtain a dibenzoyl peroxide crude product; sequentially performing washing and solid-liquid separation on the dibenzoyl peroxide crude product to obtain the dibenzoyl peroxide. According to the method provided by the invention, the treatment capacity to mother liquor by an aftertreatment system is reduced and the yield of dibenzoyl peroxide is improved by recycling partial mother liquor formed after BPO preparation in the prior art and applying the mother liquor to the preparation of the reaction liquid.