This invention relates to a new technique for separating and purifying fatty acids from soap stock of plant oil. The new technique is aimed to achieving a hydrolysis rate of 98% with mild reaction conditions. The technique comprises: (1) performing short-path distillation on acidified plant oil to separate heavy and light components; (2) performing acid-catalyzed hydrolysis on the heavy components under normal pressure to obtain crude fatty acids; (3) performing short-path distillation to obtain purified fatty acids. The light components are mainly fatty acids, thus can reduce the contents of fatty acids in the acidified plant oil and realize rapid and high-efficiency hydrolysis of grease. The reactions are performed at 120 deg.C under normal pressure, thus can reduce the requirements on the equipment. |