We　propose　a　theoretical　scheme　to　observe　the　loss　of　quantum　coherence　through　the　coupling　of　the　superconducting　charge　qubit　system　to　a　nanomechanical　resonator　(NAMR),　which　has　already　been　successfully　fabricated　in　experiment　and　is　convenient　to　manipulate.　With　a　similar　form　to　the　usual　cavity　QED　system,　this　qubit-NAMR　composite　system　with　engineered　coupling　exhibits　the　collapse　and　revival　phenomenon　in　a　progressive　decoherence　process.　Corresponding　to　the　two　components　of　superposition　of　the　two　charge　eigenstates,　the　state　of　the　nanomechanical　resonator　evolves　simultaneously　towards　two　distinct　quasi-classical　states.　Therefore　the　generalized　＂which　way＂　detection　by　the　NAMR　induces　the　quantum　decoherence　of　the　charge　qubit.