Provided are nonvolatile memory devices and program methods thereof. A nonvolatile memory device provides a program voltage to a selected word line and performs a program verify operation. The nonvolatile memory device controls a bit line voltage of the next program loop according to the program verification result. In the program verification operation, a target verify voltage is used as a pre-verify voltage. The nonvolatile memory device controls the bit line voltage of the next program loop according to the program verification result, thus making it possible to reduce the threshold voltage distribution of a memory cell. Also, the nonvolatile memory device uses the target verify voltage as the pre-verify voltage, thus making it possible to increase the program verification speed.