Bolted　joints　frequently　experience　loosening　in　vibrating　environments,　posing　a　threat　to　structural　safety.　Therefore,　quantitatively　assessing　bolt　loosening　is　critical.　This　study　reveals　the　correlation　between　bolt　preload　and　acoustic　emission　(AE)　signal　characteristics　at　the　connection　interface　under　vibration,　establishing　a　method　for　quantitatively　assessing　the　tightening　state　of　bolted　joints.　First,　an　AE　testing　platform　was　constructed　to　capture　AE　signals　across　varying　preload　forces,　enabling　the　calculation　of　frequency　and　energy　parameters.　Next,　leveraging　the　relationship　between　these　AE　characteristics　and　preload　force,　a　loosening　index　was　developed　to　quantitatively　assess　the　extent　of　bolt　loosening.　Finally,　a　quantitative　AE-based　assessment　method　and　workflow　for　evaluating　bolted　joint　status　were　developed,　allowing　for　effective　assessment　of　the　full　transition　from　tightened　to　loosened　states.　This　approach　provides　a　valuable　tool　for　detecting　bolt　loosening　and　monitoring　structural　health.