Abstract: The progress of study on biosynthesis and physiological function of digalactosyl diacylglycerol (DGDG) of photosynthetic membrane is reviewed in this paper. DGDG is the unique digalactolipid in photosynthetic membrane. It is extensively distributed in different domains of photosynthetic membrane. Two biosynthesis pathways of DGDG are present in higher plant chloroplasts, namely the prokaryotic and eukaryotic pathway. The prokaryotic pathway is restricted to the plastid, whereas the eukaryotic pathway involves reactions at the plastid and the endoplasmic reticulum. It is well established that DGDG plays an important role in maintaining oligomer structure of light-harvesting complex of photosystem Ⅱ (PSⅡ) and regulating the activity of the oxygen evolution in PSⅡ or PSⅡ core complex.