In this report, current-voltage (I/V) curves, output luminance of the OLEDs (organic light emitting diodes) with nitrogen (N2) doped ETL (electron transport layer) have been studied in detail. Experimental results show that the turn on voltage and driving voltage of OLEDs with ETL evaporated in the optimum N2 gas ambient pressure of 1times10-4 torr are reduced from 3.5 V to 1 V and 7.7 V to 5.7 V, respectively. The significant improving mechanism has been illustrated comprehensively with a schematic energy diagram model.