Investigation　of　the　nonlocality　evolution　of　entangled　mesoscopic　fields　under　decoherence　not　only　is　important　for　understanding　the　quantum-classical　transition,　but　also　has　relevance　to　quantum　communication　and　quantum　computation　protocols　based　on　continuous　variables.　According　to　previous　formulations　of　Bell　inequalities,　the　system　loses　nonlocal　features　far　before　the　disappearance　of　entanglement.　We　here　construct　a　new　version　of　Bell　signal　based　on　rotated　and　displaced　on-off　correlations,　with　which　the　Bell　inequality　is　violated　as　long　as　there　remains　entanglement　and　the　field　state　components　keep　quasiorthogonal.　Consequently,　the　nonlocal　character　revealed　by　our　formulation　decays　much　slower　compared　with　those　based　on　previous　ones.　More　importantly,　there　exists　a　wide　regime　where　the　Bell　inequality　is　restored　with　previous　formulations　but　remains　to　be　violated　based　on　our　correlation　operators.