A programming method of a non-volatile memory device includes a pre-program of the non-volatile memory device, and a main-program of the pre-programmed non-volatile memory device. The non-volatile memory device may include a tunnel dielectric layer, a charge storage layer, a blocking dielectric layer, and a gate electrode, which are sequentially stacked on a semiconductor substrate. The charge storage layer may be an electrically-floated conductive layer, or a dielectric layer having a trap site. By performing a main-program after performing a pre-program, to increase the threshold voltage of the non-volatile memory device, the program current can be effectively reduced.