NOVELTY - Preparation of sulfonic acid group-containing polycarboxylate dispersing agent involves dissolving 2-acrylamido-2-methylpropanesulfonic acid in water, adding chain transfer agent, heating under stirring, controlling the temperature to 55-60 degrees C, removing oxygen-nitrogen, heating to 62-68 degrees C, adding monomer aqueous solution (A) containing acrylic acid and acrylic-1-hydroxypropyl acrylate, and initiator aqueous solution (B), heating, reacting, naturally cooling to less than 30 degrees C, adjusting pH of reaction solution to 7-8 using sodium hydroxide solution, and obtaining polymer solution.    USE - Preparation of sulfonic acid group-containing polycarboxylate dispersing agent used for dispersing iron oxide, titanium dioxide and atrazine in circulating water.    ADVANTAGE - The method enables safe and environment-friendly preparation of sulfonic acid group-containing polycarboxylate dispersing agent having excellent heat resistance, salt tolerance and environmental adaptability, by a simple process in a short period of time.    DETAILED DESCRIPTION - Preparation of sulfonic acid group-containing polycarboxylate dispersing agent involves dissolving 2-acrylamido-2-methylpropanesulfonic acid in water, adding chain transfer agent, heating under stirring, controlling the temperature to 55-60 degrees C, removing oxygen-nitrogen, heating to 62-68 degrees C, adding monomer aqueous solution (A) containing acrylic acid and acrylic-1-hydroxypropyl acrylate, and initiator aqueous solution (B), heating to 70-90 degrees C, keeping the temperature, reacting for 1-3 hours, naturally cooling to less than 30 degrees C, adjusting pH of reaction solution to 7-8 using sodium hydroxide solution, and obtaining polymer solution. The sulfonic acid group-containing polycarboxylate dispersing agent contains 30-55 %mass acrylic acid, 15-40 %mass acrylic-1-hydroxypropyl acrylate and 15-50 %mass 2-acrylamido-2-methylpropanesulfonic acid based on 100 %mass monomer composition.