Ethanol　has　a　characteristic　narrow　band　absorption　peak　(2989.6　cm-1)　that　overlaps　heavily　with　the　airborne　water　vapour　spectrum,　severely　affecting　detection　accuracy　when　the　ambient　humidity　varies　significantly.　To　this　end　it　is　particularly　critical　to　investigate　a　method　to　eliminate　background　effects　and　improve　the　accuracy　of　ethanol　telemetry.　Firstly,　the　second　harmonic　signal　of　ethanol　concentration　under　5000~20000ppm*m　water　vapour　environment　was　simulated　by　multi-functional　fitting　method,　and　the　multivariate　linear　relationship　between　the　second　harmonic　amplitude　and　water　vapour　concentration　and　ethanol　concentration　is　obtained.　Two　sets　of　signals　were　obtained　in　one　triangular　wave　period　using　double　modulated　amplitude　and　linear　regression　was　used　to　solve　the　coefficients　of　the　two　equations,　which　in　turn　inverted　the　ethanol　concentration　in　other　water　vapour　environments.　Simulation　results　show　that　the　maximum　error　is　less　than　2.23ppm*m.　The　method　also　eliminates　the　need　for　complex　reference　light　paths　or　expensive　wide-range　tunable　mid-infrared　lasers,　reduces　measurement　errors　due　to　variations　in　ambient　humidity,　and　provides　a　basis　for　further　development　of　simple,　miniaturised　ethanol　telemetry　systems.　©　2023　SPIE.