NOVELTY - Tin chloride is dissolved in water, and hydrochloric acid is added and stirred. Activated alumina template is added to the obtained solution and dried, to obtain an alumina template containing tin chloride particles in pores. The template is calcined to oxidize tin chloride into tin oxide, placed in a tubular furnace, and acetylene gas is supplied. The material is heated to obtain a carbon nanotube structure, stirred in sodium hydroxide to completely remove template, filtered, and dried to obtain a carbon nanotube/tin dioxide composite as a gas sensor.    USE - Manufacture of tin dioxide/carbon nanotube gas sensor used for detecting methane gas.    ADVANTAGE - The method enables simple, convenient and economical manufacture of tin dioxide/carbon nanotube gas sensors having excellent selectivity and sensitivity with respect to methane gas.    DETAILED DESCRIPTION - An alumina template is activated by preprocessing at high temperature in a muffle furnace. Tin chloride nonahydrate is dissolved in distilled water, and hydrochloric acid is added and magnetically stirred to prevent hydrolysis of tin chloride. The activated alumina template is added to the obtained solution and vacuum-treated to impregnate tin chloride into the template. The template is then removed and dried, to obtain an alumina template containing tin chloride particles uniformly distributed in the pores of template. The template is placed in a muffle furnace and calcined at 600 degrees C or less to oxidize tin chloride into tin oxide. The material is placed in a chemical vapor deposition tubular furnace, acetylene gas is supplied for 5 minutes, and air and other gases are expelled from the tube. The material is then heated in air at 800 degrees C such that acetylene gas enters the pores of template. The material is heated in the absence of oxygen at high temperature, to form carbon attached to the pore inner surface and obtain a carbon nanotube structure. Tin oxide is embedded in the inner wall of carbon nanotube structure. The material is put into 0.5 mol/L sodium hydroxide and magnetically stirred for 6 hours, to completely remove the template. The obtained solution is filtered and dried to obtain a carbon nanotube/tin dioxide composite as a gas sensor.