The present invention is related to a method for purifying crude α-sulfo fatty acid salt obtained by the reaction of fatty acid and sulfur oxides, comprising the following steps: a) diluting the crude α-sulfo fatty acid in a solvent and adjusting the ph from 2 to 4; b) heating up the slurry of a-sulfo fatty acid salt obtained in the step a) until being fully solubilized: c) cooling down the solution of α-sulfo fatty acid salt obtained in the step b) to room temperature gradually to obtain the crystals; d) filtering the crystal obtained in the step c) to remove the motherinsing the filter cake at least twice with acid aqueous solution to obtain the purified α-sulfo fatty acid salt.