After　the　lean　fuel　premixed　combustion　technology　is　applied　to　aero　engines,　severe　combustion　oscillations　will　be　cased　and　led　to　hidden　safety　hazards　such　as　engine　vibration,　further　energy　waste　and　other　problems.　Therefore,　it　is　increasingly　important　to　actively　control　combustion　oscillations.　In　this　paper,　a　multispectral　radiation　thermometry　(MRT)　is　used　to　analyze　the　hydroxyl　group,　which　is　a　measurable　research　object　in　the　combustion　chamber　of　an　aero　engine,　and　to　fit　the　functional　relationship　between　the　radiation　intensity　ratio　and　the　temperature　in　different　bands.　The　theoretical　value　of　the　error　is　＜2%.　At　the　same　time,　in　order　to　solve　the　problem　of　weak　detection　signal　and　excessive　interference　signal,　an　improved　frequency　domain　filtering　method　based　on　fast　Fourier　transform　is　designed.　Besides,　the　FPGA　platform　is　used　to　ensure　the　real-time　performance　of　the　temperature　measurement　system,　and　simulations　and　experiments　are　performed.　An　oscillating　signal　with　an　oscillation　frequency　of　315　Hz　is　obtained　on　the　established　test　platform,　and　the　error　is　only　1.42%.