Stay　cables　are　the　most　critical　structural　components　in　modern　cable-stayed　bridges.　The　cable　tension　plays　an　important　role　in　the　construction　control　and　long-term　monitoring　of　cable-stayed　bridges.　Experimental　vibration　measurement　is　one　of　the　most　widely　used　methods　for　tension　evaluation　and　condition　assessment　of　cable-stayed　bridge.　There　is　a　unique　relationship　between　the　tension　force　and　fundamental　frequency　of　the　stay　cable.　The　key　to　success　of　this　technique　is　the　accuracy　of　identified　fundamental　frequency　of　each　stay　cable.　In　this　paper,　experimental　modal　analysis　of　bridge　stay　cables　is　carried　out　using　output-only　acceleration　records　of　the　stay　cables.　An　automated　data　analysis　approach　to　determine　cable　fundamental　frequency　is　proposed　with　the　power　spectral　density　(PSD)　and　cepstrum　method.　Application　of　the　automated　data　analysis　approach　to　the　Jinma　Bridge　cables　in　Guangdong　Province　of　China　where　test　was　carried　out　using　ambient　vibration　measurement　demonstrated　high　identification　accuracy　and　confidence　of　this　technique.