A　set　of　Bell　inequalities　classifying　the　quantum　entanglement　of　four-qubit　states　is　presented.　These　inequalities　involve　only　two　measurement　settings　per　observer　and　can　characterize　fully　separable,　bi-separable　and　tri-separable　quantum　states.　In　addition,　a　quadratic　inequality　of　the　Bell　operators　for　four-qubit　systems　is　derived.