Disclosed is a cigarette-opening smell trapping device and its detecting method. Said trapping device comprises a trapping bottle capable of containing a package of cigarette , a top cap equipped withan intake port and a trapping port, and an intake tube, wherein the top cap and the trapping bottle are combined firmly, the intake tube is set inside the intake port and is in closed combination with the intake port, one end of the intake tube goes deep into the trapping bottle. Said detection process is as follows: package-opening a cigarette and rapidly put it into a trapping bottle, coving the bottle with the top cap, inserting the intake tube and the trapping therein, connecting the intake tube and the trapping tube respectively with an air-intake installation and a sampling unit; through the air-intake installation, introducing the treated gas fluid into said trapping bottle bottom part through the intake tube, and driving the package-opening smell to outflow from the trapping tube;sampling the effluent package-opening smell through a sampling unit connected with the trapping tube, executing qualitative and quantitative analysis and detection by using a thermal desorption-gas chromatography-mass spectrometry method. Through the present invention, one can simply and accurately execute cigarette-opening smell trapping and detecting.