A multiphasic buffer system was used to seperate the human short tandem repeat DNA fragments.In stacking gel the main content of buffer were bistris,sulfuric acid and bicine while tris, sulfuric acid and bistris play a major role in seperating gel.The DNA fragments,which can be stacked efficiently in stacking gel and destacked completely in seperating gel, were seperated according to their size. By this way the high-resolution results can be achieved.