The invention discloses a method for preparing high specific surface area adsorbent resin by photochlorination of dimethylbenzene, which comprises the steps of: firstly, carrying out photochlorination reaction on p-xylene and chlorine which are used as basic raw materials to obtain a photochlorination product of 1,4-benzyl bichloride; secondly, adding the photochlorination product, a solvent, a catalyst or the photochlorination product, the solvent, the catalyst and a micromolecular aromatic compound into a reaction container for heating, stirring and promoting the dissolution, carrying out polymerization, then cooling to room temperature; boiling the cooled product with dilute acid, extracting by adopting an acetone solution, washing, drying to obtain the product; and measuring the specific surface area of the product by adopting a low-temperature nitrogen adsorption de-absorption method. The high specific surface area resin is prepared by using the p-xylene and the chlorine with lowcost and little toxicity as raw materials. The method for preparing the high specific surface area resin has lower production cost and little toxicity and is beneficial to protecting the environment and ensuring the health of operators.