Waterproof resin

The invention discloses a waterproof resin. The waterproof resin comprises the following components in weight percentages: 14-19% of soya oil acid, 7-13% of glycerol, 8-15% of phthalic anhydride, 2-6% of fumaric acid, 1-4% of pentaerythritol, 4-10% of rosin, 1-5% of E-20 epoxy resin, 0.1-0.5% of hypophosphorous acid, 2-6% of xylene and 40-50% of toluene; the preparation comprises the following steps: diluting the glycerol with water; adding the soya oil acid, the glycerol, the phthalic anhydride, the fumaric acid, the pentaerythritol, the rosin, the E-20 epoxy resin and the hypophosphorous acid; adding 20%-50% of the xylene to react for 0.5-1.5 hours at 170 DEG C, adding the rest xylene to react for 0.5-1.5 hours at 180 DEG C; heating to 204-208 DEG C, cooling after refluxing to an acid value not more than 4mgKOH/g and viscosity not less than 3sec/grille with water; and using toluene to dilute reaction product after cooling to below 150 DEG C.