The invention discloses a waterproof thermal insulation coating for the inner wall of a pipeline, and a preparation method thereof. The waterproof thermal insulation coating comprises, by weight, 20-40 parts of an organosilicone modified acrylic emulsion, 10-20 parts of a hydrophobically modified nanomaterial, 5-10 parts of a porous material, 2-5 parts of inorganic fibers, 5-8 parts of an inorganic filler, 2-5 parts of water glass, 0.5-2 parts of a water repellent and 15-25 parts of deionized water. The coating has excellent waterproofing and thermal insulating performances, and can meet the waterproofing and thermal insulating requirements of the inner wall of the pipeline.