Tin dioxide($_SnO2$) thin films were deposited on alumina substrate by metal-organic chemical vapor deposition (MOCVD) as a function of temperature and time. Thin films were fabricated from di-n-butyltin diacetate as a precursor and oxygen as an oxidation. The microstructure of deposited films was characterized by X-ray diffraction and field emission scanning electron microscopy(FE-SEM). The thickness was linearly increased with deposition time and $SnO_2$structure was found from $375^{circ}C$ for the deposition time of 32 min. The maximum sensitivity to 500ppm CO gas was observed for the specimens deposited at $375^{circ}C$ for 2 min at the operating temperature of $350^{circ}C$. Gas sensitivity to CO increased with decreasing the film thickness. The sensing properties of response time, recovery and sensitivity of CO were changed with variations of substrate temperature and time.