The invention discloses an organic-inorganic nano-composite reinforced polyethylene material and a preparation method thereof. The material is composed of 5-20wt% of rutile type titanium dioxide micrometer particles, 0.5-30wt% of modified carbon nanotubes, 0.5-2wt% of an antioxidant, 0.1-5wt% of an organic UV absorbent and the balance high density polyethylene. The preparation method consists of: firstly mixing sulfuric acid with nitric acid, then placing carbon nanotubes in the mixed acid to carry out stirring reaction, then performing solid-liquid separation, washing and drying treatment, then adding the obtained purified carbon nanotubes into a surface modifier solution to carry out reaction, and then performing drying to obtain modified carbon nanotubes, and then putting the rutile type titanium dioxide micrometer particles, the modified carbon nanotubes, the antioxidant, the organic UV absorbent and the high density polyethylene in a twin-screw extruder to conduct melt blending, and then performing extrusion, thus obtaining the target product. With high long-acting ultraviolet resistance, the organic-inorganic nano-composite reinforced polyethylene material can be widely used as films, pipes, wires and cables, plastic products and packaging materials under outdoor natural conditions.