A new type of semiconductor gas sensor fabricated on an alumina substrate for CO and CH_4 detection has been developed.The alumina substrate was obtained by an anodizing method companying with micromachining to form patterned structure.Gas sensitive material was made of nano-sized SnO_2 powder prepared by a chemical precipitation method.Au (0.048wt.%) and Pd (0.3 wt%) were doped to SnO_2 powder to increase sensitivity to CO and CH_4,respectively.The heating power and sensing performance were measured with an automatic test system.The results show that the sensors have remarkable responses and certain selectivity to the target gases.Our study demonstrates that alumina substrate can be successfully applied in sensor micromachining technology. A new type of semiconductor gas sensor fabricated on an alumina substrate for CO and CH_4 detection has been developed. The alumina substrate was obtained by an anodizing method companying with micromachining to form patterned structure. Gas sensitive material was made of nano-sized SnO_2 powder prepared by a chemical precipitation method. Au (0.048 wt.%) and Pd (0.3 wt.%) were added to SnO 2 powder to increase sensitivity to CO and CH 4, the heating power and sensing performance were measured with an automatic test system. results show that the sensors have remarkable responses and certain selectivity to the target gases. Our study demonstrates that alumina substrate can be successfully applied in sensor micromachining technology.