NiO@CuO nanocomposite was synthesized through a simple reflux and hydrothermal method. NiO@CuO gas sensor has been fabricated and investigated. The result revealed that the NiO:CuO molar ratio 1:1 of NiO@CuO (NC-1) sensor shows the fast response time which was 2s to 100 ppm NO2 gas at room temperature (RT), which is better from NC-2 and NC-4 which have NiO:CuO molar ratios of 2:1 and 4:1, respectively. This valuable gas sensing properties could be attributed to the combined action of the high specific surface, highly porous structure, and interactions between high conductivity of NiO nanosheets (NSs) and CuO nanoparticles (NPs), which is salutary for diffuse and adsorption-desorption of gas on the surface of the NC-1. The high gas sensing performance of NiO@CuO sensors described here will be a promising material towards the detection of NO2 gas in environmental supervising. (C) 2017 Elsevier B.V. All rights reserved.