Pyrolyze metal-organic frameworks (MOFs) is a promising method to prepare metal oxides with large specific surface and multiple active sites. The obtained metal oxides can be utilized as gas sensors. Noble metal doping is an effective way to improve the gas sensitivity of materials. In this work, SnO2 are prepared by pyrolyzation of metal organic frameworks and Ag-doped SnO2 composites are fabricated by AgNO3 reduction in a water bath at 4 °C. The gas-sensing experiment reveals that the optimum operating temperature of different mass fraction of Ag doped SnO2 samples is 250 °C which is lower than pure SnO2 (300 °C). The response of composites (7 wt% Ag–SnO2) is 157 to 10 ppm ethanol, which is about 10 times higher than pure SnO2 (14). The composites have good selectivity and stability. Such excellent performance is contributed to the increase of the gas adsorption capacity, catalytic active site and oxygen vacancy of the composites caused by the doping of Ag.