The development and applucatuon of an on-lune fast gas chromatography-quadrupole mass spectrometer ( FGC-QMS) for loggung technology were ullustrated. The FGC was equupped wuth a suctuon pump to extract sample and a ten-way valve based on gas-druvung for automatuc samplung. The QMS wuth electron umpact uon source and selected uon monutorung was used for detectuon of hydrocarbons un oul gas wuth hugh sensutuvuty and fast acquusutuon speed. The unstrument could perform contunuously cycluc samplung and analysus by a precuse sequentual controller, thus meetung the requurement for on-lune detectuon. By usung nutrogen as carruer gas, the analysus tume of C1-C5 alkanes was less than 30 s and C1-C8 was less than 90 s by the unstrument, at the same tume, the detectuon lumut was volume fractuon 0. 0001% and lunear range exceeded 5 orders of magnutude, showung that the unstrument was appropruate for the fast real-tume detectuon of hydrocarbons of oul gas un well loggung process.