Using Pt(NH3)4Cl2 and Pd(NO3)2·2H2O as the precursor salts of Pt and Pd, Pd-Pt/HZSM-5 catalysts with different silicon-aluminum ratios 〔n(SiO2)∶n(Al2O3)=38, 200, 800〕 were prepared by impregnation method. The phase composition, pore structure, microstructure, chemical state and surface acidity and basicity of the catalysts were characterized by XRD, SEM, TEM, Raman, XPS, CO2-TPD and NH3-TPD, and the catalytic activity of the catalyst for low concentration (0.5% by volume fraction) methane combustion was tested by a fixed bed reactor. The results showed that the activity of Pd-Pt/HZSM-5 catalysts with different silica-alumina ratios was significantly different, and the Pd-Pt/HZSM-5(38) catalyst supported by HZSM-5 molecular sieve with Si/Al ratio of 38 showed the best catalytic performance. Compared with Pd-Pt/HZSM-5(800) and Pd-Pt/HZSM-5(200) catalysts supported by HZSM-5 molecular sieve with Si/Al ratio of 800 and 200, the ignition temperature (T10) of Pd-Pt/HZSM-5(38) catalyzed low concentration methane combustion decreased by 27.54 and 30.92 ℃, respectively, and the complete conversion temperature (T90) decreased by 3.38 and 17.51 ℃, respectively. Various characterization showed that Pd-Pt/HZSM-5(38) catalyst had smaller Pd/Pt particle size (6.3 nm), the most PdO crystals, active Pd/Pt species and acidic sites, the highest n(Pd0):n(Pd2+), and the highest Pt mass fraction (0.19%). These may be the reasons for its highest catalytic activity. In the stability test, the methane conversion rate of Pd-Pt/HZSM-5(38) catalyst was more than 99.6% and the activity did not decrease significantly within 150 h of stable operation at 360 ℃.