Prestress　loss　evaluation　in　prestressed　strands　is　essential　for　prestressed　structures.　However,　the　sensors　installed　outside　the　duct　can　only　measure　the　total　prestress　loss.　The　sensors　attached　on　strands　inside　the　duct　also　have　several　problems,　such　as　inadequate　durability　in　an　aggressive　environment　and　vulnerability　to　damage　during　tensioning.　This　paper　proposes　a　new　installation　method　for　long-gauge　fiber　Bragg　grating　(LFBG)　sensors　to　prevent　accidental　damage.　Then　the　itemized　prestress　losses　were　determined　in　each　stage　of　the　pre-tensioning　and　post-tensioning　according　to　the　LFBG　measurements.　We　verified　the　applicability　of　the　LFBG　sensors　for　prestress　monitoring　and　the　accuracy　of　the　proposed　prestress　loss　calculation　method　during　pre-tensioning　and　post-tensioning.　In　the　pre-tensioning　case,　the　calculated　prestress　losses　had　less　deviation　from　the　true　losses　than　those　obtained　from　foil-strain　gauges,　and　the　durability　of　the　LFBG　sensors　was　better　than　foil-strain　gauges,　whereas　in　post-tensioning　case,　the　calculated　prestress　losses　were　close　to　those　derived　from　theoretical　predictions.　Finally,　we　monitored　prestress　variation　in　the　strand　for　90　days.　The　itemized　prestress　losses　at　each　stages　of　post-tensioning　were　obtained　by　the　proposed　calculation　method　to　show　the　prospect　of　the　LFBG　sensors　in　practical　evaluation.