In a method of programming in a nonvolatile memory device, channels of a plurality of cell strings are precharged through ground selection transistors by a precharge voltage of a source line. A turn-on voltage is applied to a selected ground selection transistor of a selected cell string among the plurality of cell strings, during a verification read period of an N-th program loop. The turn-on voltage applied to the selected ground selection transistor is maintained to precharge the channels for an (N+1)-th program loop, without recovery after the verification read period of the N-th program loop is finished. Power consumption is reduced and an operation speed is increased by maintaining the turn-on voltage of the selected ground selection line to precharge the channels of the cell strings without recovery after the verification read operation is finished.