The invention discloses an oil-soluble mounting medium for bottom water reservoir fracturing, and belongs to the field of oilfield production. The mounting medium comprises, by mass, 5-10% of a framework material, 15-20% of rosin resin, 5-10% of dammar resin, 15-25% of petroleum resin, 8-12% of oil-soluble phenolic resin, 15-20% of terpene resin, 6-12% of petroleum asphalt, 2-4% of polyethylene, and the balance of a density regulator, wherein the framework material is ceramsite, and the density regulator is barite or calcium carbonate. The product has a high plugging strength, prevents bottomwater from coning, and can achieve water production control and oil production increase. A preparation method of the product comprises the following steps: mixing and crushing the rosin resin, dammarresin, petroleum resin, oil-soluble phenolic resin, terpene resin, petroleum asphalt and polyethylene wax, heating the obtained mixture until the mixture is completely melted, adding the framework material and the density regulator at a constant temperature, kneading the obtained mixture until the material is uniformly mixed, pouring the mixture into a container, naturally cooling the mixture to room temperature, and breaking, crushing and sieving the mixture. The preparation method has the advantages of simplicity and easily available raw materials.