Because　carbon　nanotube　(CNT)　films　have　high　photothermal　conversion　efficiency　(PTCE),　they　have　been　widely　used　in　bolometric　and　photothermoelectric　photodetectors,　seawater　desalination,　and　cancer　therapy.　Here,　we　present　a　simple,　quick,　and　non-destructive　method　to　measure　the　PTCE　of　CNT　films.　According　to　the　linear　relationship　between　the　Raman　shift　of　the　G(+)　peak　and　the　temperature　of　a　CNT,　the　offset　of　the　G(+)　peak　under　varying　excitation　light　power　can　characterize　the　changed　temperature.　Combining　the　simulation　of　the　temperature　distribution,　the　final　value　of　the　PTCE　can　be　obtained.　Finally,　a　CNT　film　with　a　high　PTCE　was　chosen　to　be　fabricated　as　a　bolometric　photodetector;　a　quite　high　responsivity　(2　A　W-1　at　532　nm)　of　this　device　demonstrated　the　effectiveness　of　our　method.