It　can　promptly　detect　hot-spot　in　the　operation　of　the　generator　by　real-time　monitoring　of　the　operating　temperature　of　the　windings　in　the　hydromotor,　thereby　ensuring　the　safe　operation　of　the　hydromotor.　To　overcome　the　limitation　of　the　sensing　temperature　measurement　distance　of　the　down-conversion　fluorescence　optical　fiber　temperature　sensor　does　not　exceed　30　meters,　a　method　was　proposed　to　use　a　semiconductor　laser　with　the　wavelength　of　1550nm　which　was　a　low　loss　in　optical　fiber　as　the　excitation　source　to　generate　upconversion　fluorescence　for　an　optical　fiber　temperature　sensor.　Upconversion　materials　ZnF2:　Er3+,　Yb3+　were　selected　as　the　fluorescent　materials　for　the　sensor.　An　experimental　device　was　constructed,　and　the　upconversion-fluorescence　lifetime　and　the　temperature　were　tested　and　calibrated.　The　results　showed　that　the　optical　fiber　temperature　measurement　distance　of　this　method　can　reach　to　76　m,　meeting　the　demand　for　the　temperature　monitoring　of　the　hydromotor　windings.　©　The　Authors.