NOVELTY - A palladium nanometer/multi-wall carbon nanometer tube is obtained by chemically bonding the multi-wall carbon nanometer tube (MWCNTs) with 1,6-hexane diamine to generate MWCNTs-1,6-hexane diamine, and then bonding the MWCNTs-1,6-hexane diamine with palladium nanometer particles through arc electron on amino group.    USE - Palladium nanometer/multi-wall carbon nanometer tube for the detection of methane.    ADVANTAGE - In the multi-wall carbon nanometer, the palladium nanometer particles have good dispersing property and small particle diameter.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) a method for preparing the palladium nanometer/multi-wall carbon nanometer tube comprising adding multi-wall carbon nanometer tube (1-3 g) into concentrated nitric acid (100 ml), agitating and refluxing for 2-4 hours, filtering, and washing with secondary distilled water; adding oxidized multi-wall carbon nanometer tube into the mixed solution of thionyl chloride and N,N-dimethyl formamide having a volume ratio of 10-20, making the multi-wall carbon nanometer tube reach 0.1-0.5% in the mixed solution, and then ultrasonically dispersing, agitating for 10-20 hours at 60-80 degrees C, filtering, washing and drying; adding the acylated multi-wall carbon nanometer tube and hexane diamine into the secondary distilled water, making the mass concentrations be 0.5-10% and 0.2-10% respectively, heating and refluxing, agitating for 4-5 hours continuously, filtering, washing and drying, and obtaining the aminated multi-wall carbon nanometer tube; preparing palladium chloride aqueous solution (0.1 mol/L) and dimethyl formamide ultrasonic dispersing solution (0.1-0.3 mol/L) of aminated multi-wall carbon nanometer tube, and then mixing the two solutions according to volume ratio that is 1:1, and then adding sodium borohydride aqueous solution (1-2 mol/L) under violent stirring, where volume ratio of the sodium borohydride aqueous solution to palladium chloride aqueous solution is 1:3, continuing agitating for 30-60 minutes, centrifuging, washing and drying to obtain the palladium nanometer/multi-wall carbon nanometer tube; and    (2) a methane detection device comprising a gas flow meter, a gas chamber and a data collection system, where substrate of the palladium nanometer/multi-wall carbon nanometer tube is provided in the gas chamber.