In this experiment， the peanut oil diglyceride was purified by molecular distillation technology， and the changes of glyceride composition， fatty acid composition， harmful substances and nutrients before and after synthesis and purification were studied. The results showed that the diglyceride with a purity of 85% and a yield of 18.54% could be obtained after secondary molecular distillation at 220 ℃. The fatty acid composition after molecular distillation did not change much， and saturated fatty acids increased. The content of trans fatty acids was low， only increasing from 0.75% to 1.2%. When the temperature exceeded 220 ℃， the content of glycidyl ester increases sharply， so the temperature of the secondary molecular distillation should not exceed 220 ℃. The physicochemical properties of peanut oil diglyceride meet the national standards. The nutrients will be reduced before and after molecular distillation， and a small amount of nutrients need to be added. This study provides theoretical support for plant technology of the purification of diglycerides by molecular distillation.