Digital　temperature　sensors　based　on　a　ring　oscillator　were　used　to　monitor　the　temperature　distribution　of　a　FPGA　chip　during　operation.　The　FPGA　has　a　high　requirement　for　real-time　data,　but　high　real-time　data　requires　a　large　number　of　logic　resources,　which　will　have　a　negative　impact　on　the　FPGA＇s　capabilities.　To　address　this　problem,　this　paper　proposes　an　online　monitoring　system　based　on　parallel　mode,　using　a　linear　feedback　shift　register　(LFSR)　to　generate　pseudo-random　numbers　as　the　frequency　counter　for　the　system,　which　solves　the　problem　of　excessive　consumption　of　logic　resources　brought　by　the　traditional　binary　frequency　counter,　while　allowing　counters　to　be　configured　independently　for　all　digital　sensors　to　achieve　parallel　measurement.　Parallel　mode　gives　a　greatly　improved　measurement　speed　over　serial　mode.　This　system　achieves　a　balance　between　real-time　data　and　resource　consumption　and　allows　online　monitoring　of　changes　in　the　internal　temperature　distribution　of　the　FPGA　chip.　©　2021　IEEE.