With the discovery of carbon nanotubes (CNTs), many applications have been implemented based on their unique electronic, mechanical, chemical and optoelectronic properties. In our work, the focus is on the fabrication of carbon nanotube (CNT) cantilever sensors for integration with CMOS readout chip which offer increased sensitivity. The higher surface-to-bulk ratio enhances the property and performance of the gas sensor by nanocantilevers. In this work, we present the detection method based on the change in capacitance of the single walled carbon nanotube (SWCNT) cantilever.The capacitance variation technique of measuring cantilever deflection was used to measure the bending rate. The capacitance between the cantilever and the fixed electrode varies as a function of the magnitude of the bending of the cantilever which is in turn proportional to the concentration of the gas species in the surrounding environment. To measure the variation in the capacitance value, the CNT cantilever beam is considered as one of the electrodes of the capacitor and the metal film as the other. The air between the plates acts as the dielectric material.