SnO₂ nanoparticles were prepared by oxidation process in liquid and Pd-loaded SnO₂ nano-sized material by im-pregnation method was synthesized.Gas sensors based on Pd-loaded SnO₂ nanoparticles were prepared by screen-printing and coated with an overlayer of zeolite layer.Based on the dynamic gas sensing test system,the sensitivity of the gas sensor for me-thane and its selectivity under the interference of CO and ethanol gas were investigated.The results showed that after printing Pd-HZSM5 layer on the surface of Pd-SnO₂ sensitive layer,the response ability of the sensor for methane was significantly improved,and the selectivity to methane was also significantly improved in the presence of 5×10^-4（volume fraction）CO.Simila-rly,in the presence of 2×10^-5（mass fraction） ethanol,the sensor response to methane was not disturbed.Through the character-ization and catalytic analysis of the molecular sieve,it was found that the catalytic efficiency of Pd-HZSM5 for CO reached 100%,which led CO be catalytically oxidized in the diffusion process.This may be the main reason for printing the Pd-HZSM5 molecular sieve membrane to improve the selectivity of the sensor.Meanwhile,the research also showed that printing molecular sieve layer on the surface of the sensitive layer will not affect the response and recovery rate of the sensor.