A driving circuit of display. Two more thin film transistors is added to the original driving circuit of display so that the driving circuit now includes four thin film transistors such that the gate terminal of the thin film transistor's voltage level increases as the threshold voltage of the driving thin film transistor increases. The driving current of the thin film transistor is able to maintain a constant value so that the initial luminance of the display remains unchanged. Therefore, the present invention can effectively increase the average working life of the display.