The gas sensors are fabricated from multiwalled carbon nanotube-based. The electrode is constructed from platinum (Pt) and titanium (Ti). The gas sensors are used for detecting oxygen (O2), ethyl alcohol (C2H5OH) and ammonia (NH3) by measuring the charge of their electrical capacitance. In the ratio silicon dioxide (SiO2) : carbon nanotube (MWCNTs) = 100:1 by weight, the electrical capacitance of the film layer has changed at the highest rate. The response of oxygen with concentration of 10,000 ppm, 20% of ethyl alcohol and 20% of ammonia, it is found that the electrical capacitance of thin layer has change about 34%, 60% and 70%.