The invention discloses a preparation method of gel type strong-base styrene anion exchange resin. The gel type strong-base styrene anion exchange resin disclosed by the invention is prepared by taking styrene, divinyl benzene, benzoyl peroxide, polyvinyl alcohol, gelatin, methylene blue, dichloromethane, 1,4-dichloromethoxybutane, anhydrous stannic chloride and trimethylamine as main raw materials through suspension polymerization reaction, chloromethylation reaction and amination reaction. The preparation method disclosed by the invention comprises the following steps of carrying out suspension polymerization reaction to synthesize a styrene-divinyl benzene cross-linked polymer, carrying out chloromethylation reaction of the styrene-divinyl benzene cross-linked polymer, and carrying out amination reaction of a chloromethylated styrene-divinyl benzene cross-linked polymer. The particle size range of the resin prepared by the method is 0.5-1.5 mm; the resin has a good property of removing sulfate and nitrate, a relatively high regeneration rate and the like; various physicochemical properties of the resin are good. Therefore, the resin disclosed by the invention can be applied in the sulfate and nitrate removing treatment process of water, and has good development prospects and practical significance.