The invention discloses a transformer sound insulation shell material and a preparation method thereof, which belong to the field of materials and solve the problem of poor sound insulation effect of existing materials. The preparation method specifically comprises the following steps of adding bakelite, epoxy resin, glass fibers, chemigum, polyvinyl chloride resin, cenosphere, expanded vermiculite, calcium carbonate, diatomaceous earth, silicone oil and antioxygen into a container, stirring for 15 to 20 minutes at the rotating speed of 1600 to 1900 r/min, uniformly mixing, then adding dichloromethane, continuously stirring for 5 to 10 minutes, adding acetic acid at last, stirring for 5 to 10 minutes at the rotating speed of 2000 to 2200 r/min, pouring raw materials which are uniformly mixed into a mold, solidifying for 60 to 80 minutes at the temperature of 65 to 75 DEG C, cooling and demolding, so as to obtain the transformer sound insulation shell material. The preparation method has the advantages of simplicity, easiness in operation and low production cost and can be widely used for transformer shell and case materials.