The invention discloses a superhydrophobic visible light photocatalytic self-cleaning coating layer and a preparation method thereof. The method comprises the steps: firstly, treating a substrate, andthen preparing a micro-nano composite hierarchical structure pigment: stirring distilled water, glacial acetic acid and a bismuth source at room temperature to obtain a homogeneous and transparent solution A; adding a halogen source solution to the solution A while stirring, adding sodium borohydride and an alcohol solution, filtering after stirring under the condition of the temperature of 25-100 DEG C, washing, and drying, to obtain bismuth oxyhalide 3D microspheres with a micro-nano composite hierarchical structure; and then carrying out hydrophobic modification of the micro-nano compositestructure pigment, compounding with a superhydrophobic coating, and coating. The contact angle of a prepared superhydrophobic coating layer is more than 150 DEG, the rolling angle is less than 10 DEG, dust and other inorganic dirt can be brought away with the help of water scouring, and organic pollutants can be degraded under illumination of visible light, so the superhydrophobic and self-cleaning functions of the substrate are realized.