In view of rapid protection requirements of large two-winding transformer， both sides sampling currents of two-winding transformer， their mutational quantity sequence phase characteristics and the characteristics of sampling current（voltage） absolute positive（negative） mutation are analyzed. Also， the protection principle to fast remove serious transformer fault based on sampling value information under power supply on single and on both side is introduced. The protection principle has some good characteristics such as simple algorithm， fast operation speed， high sensitivity， large phase discrepancy permission between current transformers on both sides of transformer and strong ability to resist current transformer saturation， etc. In addition， it has unique advantages in solving special problems such as inrush current impact on transformer protection， malfunction of instantaneous current differential protection when current transformer is in serious saturation.