The invention belongs to the technical field of polymer purifying operation, and particularly relates to a zone melting method for purifying polymer polyethylene glycol. The method comprises the stepsof: dissolving two or more PEG with different molecular weights in deionized water completely so as to obtain a solution, and keeping the solution standing; taking supernatant of the solution in a zone melting test tube, and performing condensation treatment until the supernatant in the zone melting test tube is solidified completely; performing a zone melting purification experiment after the condensation treatment is conducted, and adjusting the experimental temperature at 40-45 DEG C, the experiment speed at 8-10 mm/h and the number of zone melting times at 5 for a purifying device; dividing the zone melting tube tube into sections so as to obtain 8 sections of samples, and labeling the samples; removing deionized water in each section, dissolving 4 mg of each section of the samples in5ml THF, and performing GPC detection separately. Through the method, the problems of thermal decomposition of organic polymer materials, adverse solid-liquid interface transfer, which is caused by excessive viscosity, of impurities and the like are solved for conventional zone melting purification, and therefore the method has a more practical value.