To　further　evaluate　the　corrosion　conditions　of　steel　bars　in　RC　structures,　the　monitoring　and　location　technology　for　the　corroded　steel　bars　in　RC　beams　was　investigated　based　on　piezoelectric　sensors.　Firstly,　three　pairs　of　piezoelectric　lead　zirconate　titanate　(PZT)　sensors　were　arranged　on　the　surface　of　the　steel　bar,　then　the　monitored　signals　were　processed　by　Radix-4　FFT,　and　the　frequency　spectrum　features　were　extracted　to　figure　out　the　development　trend　of　the　corrosion　process.　Meanwhile,　the　applicability　of　the　PZT-based　monitoring　method　for　the　overall　corrosion　process　of　steel　bars　was　verified.　Secondly,　for　the　purpose　of　locating　the　corrosion　positions　of　the　steel　bar,　the　weight　function　of　the　probabilistic　imaging　method　was　modified　to　obtain　the　position　image　of　the　corroded　steel　bar.　Finally,　the　peak　signal　in　the　frequency　domain　was　analyzed,　and　the　relationship　between　the　damage　factor　(FDI)　and　the　corrosion　rate　was　established　to　quantify　the　corrosion　degree　of　the　steel　bar.　Results　show　that　the　corrosion　process　of　steel　bars　in　RC　beams　could　be　divided　into　three　phases:　depassivation　phase,　debonding　phase,　and　failure　phase;　the　proposed　damage　factor　(FDI)　could　effectively　depict　the　three　phases　in　the　corrosion　process　of　steel　bars　and　quantify　the　corrosion　rate　of　steel　bars;　the　probabilistic　imaging　method　could　realize　whole-process　monitoring　and　analyze　the　corrosion　positions　of　the　steel　bars.　It　indicates　that　the　monitoring　technology　and　the　probabilistic　imaging　method　can　accurately　monitor　the　overall　process　and　locate　the　corrosion　positions　of　steel　bars　in　RC　structures.　The　relationship　between　each　phase　of　the　whole　process　and　the　damage　factor　(FDI)　can　quantify　the　steel　corrosion　rate,　which　can　provide　technical　support　for　the　safety　assessment　of　RC　structures.　Copyright　©2022　Journal　of　Harbin　Institute　of　Technology.All　rights　reserved.