The invention discloses a synthetic method of pollution-resistant deeply-softened chelating resin. The synthetic method comprises the following steps: preparing an oil phase by adopting a styrene monomer, a divinyl benzene crosslinking agent, a pore-foaming agent and an initiating agent; preparing a water phase by adopting water, a dispersant and NaCl; adding the oil phase into the water phase, lowering the temperature after a temperature rising process, discharging, washing, extracting, drying and screening to obtain polystyrene series styrene-divinylbenzene copolymers of the pollution-resistant deeply-softened chelating resin; then performing chloromethylation reaction, and transforming to obtain polystyrene series chloromethylated beads; performing stirring expansion on the polystyrene series chloromethylated beads by using dichlorethane, adding N-hydroxymethyl phthalimide, dropwise adding a catalyst, heating, preserving the temperature, cooling, pumping out mother liquor, adding water, performing reduced pressure distillation, and cleaning; and adding 25% caustic soda liquid, heating, stabilizing, washing with water, adding a chloroacetic acid solution to perform chelation reaction, heating, preserving the temperature, washing with water, performing acid regulation, washing with water, performing alkali regulation, washing with water until the mixture is neutral, and discharging for package to obtain the pollution-resistant deeply-softened chelating resin.