Nanocrystalline semiconducting Cu2S films have been prepared onto corning glass substrates using chemical bath deposition (CBD) and modified chemical bath deposition(M-CBD) methods. In chemical bathdeposition (CBD), preparative parameters such as concentration, deposition time, complexing agent and pH of the bath are optimized, while in modified chemical bath deposition (M-CBD) preparative parameters such asconcentration,immersion cycles, immersion time and rinsing time were optimized. The comparative gas sensing property study of CBD and MCBD deposited Nanocrystalline Cu2S have carried out. These as deposited Nanocrystalline semiconducting Cu2S films work assensor and gave optimum responses to different gases atdifferent operating temperatures. The surface misfits operating temperature can affect the microstructure and gas sensing performance of the sensor. The resistance responses of the nanocrystalline Cu2S thin films were measured byexposing as deposited film to different gases namely ammonia (NH3), carbon dioxide (CO2), ethanol (C2H5OH), hydrogen sulphide (H2S), liquid petroleum gas (LPG), hydrogen (H2) and chlorine (Cl2). It was found that the sen-sors exhibited various sensing responses to these gases at different operating temperature.The results demonstrated that CBD deposited nanocrystalline Cu2S thin film have more gas sensing response than MCBD Cu2S thin films and Cu2S can be used as a new type of gas sensing material which has a high sensitivity and good selectivity.