An operating method of a memory system which includes a nonvolatile memory device including memory cells connected to a plurality of word lines, the operating method including pre-charging a selected one of the plurality of word lines; detecting a variation in a voltage or a current on the selected word line after the selected word line is floated; generating runtime failure information according to the detected variation; and determining a state of the selected word line or a state of a memory block including the selected word line, based on the runtime failure information.