Metal oxide semiconductor gas sensors are one of the efficient systems in order to recognize different gases and measurement their concentration. Working base of them is the gas reaction with the surface layer atoms. This act is caused to chrome changing and banding energy level of them. At this research, the effect of operation temperature and substrate temperature on the sample is investigating in order to improving the efficiency of gas sensor. This research is include of two sections 1- Fabrication of tungsten oxide layers by flame synthesize method, accompanied by changing the substrate temperature parameter 2- investigation of tungsten oxide sensor propertie in different operation temperatures. In the first section of this research, it is taken to action fabrication of tungsten oxide thin film in flame synthesis method at different substrate temperatures (100 to 450 ?C). This action is taken place with placing tungsten rod with high sincerity in the hydrogen flame. A hydrogen flame with high temperature is accessible with action to hydrolysis water process and analyzing that to hydrogen (fuel material) and oxygen (oxidation material) and conducting them to the nozzle. With action XRD analysis, combination phase of layers that are built in substrate temperatures up to 350 ?C is equated with triclinic or anorthic. In addition, phase of layers that are built at substrate temperatures upon to 350?C are recognize the tetragonal phase. The SEM analysis is indication of porous and suitable nanostructures for gas sensing application up to 350 ?C. In the second section of research, with pay attention to suitable results of SEM analysis, it is act to building a system in order to studying of tungsten oxide sensor properties. By this system, different temperatures (operation temperature) was given to tungsten oxide layers at the time of giving gas. Thus, in order to finding the optimize properties of gas sensing, the effect of substrate temperature and operation temperature on the tungsten oxide sensor properties was study.
