A method of operating a data storage device includes setting program verify voltages for verifying whether memory cells of a nonvolatile memory device are programmed to desired program states; transmitting the set program verify voltages to the nonvolatile memory device; generating data patterns respectively corresponding to program states based on the program verify voltages; transmitting a data pattern corresponding to the program verify voltages to the nonvolatile memory device; and programming the memory cells with the transmitted data pattern.