A novel technique for power electronic switch current detection is introduced in this paper, in which the current-sensor is replaced by electronics circuit. According to the principle that the magnitude of the switch current is proportional to its turned-on voltage drop, the proposed technique utilizes the method of grasping the turned-on voltage drop of the MOSFET to reproduce its current waveform. The appearances of voltage drop of the MOSFET are analyzed and the current reconstruction principles are introduced. Experimental results are given to validate the proposed technique. It has the characteristics of simplicity and inexpensiveness and is worthy of adoption.