In this paper, n-porous silicon/n-WO3 nanowires composite was prepared by a two-step heating process of as-sputtered W film on the nano-porous silicon (PS), and the effect toward sensing response characteristics of NO2 gas was studied. The morphology and crystal structure of samples were investigated by means of FESEM, TEM and XRD. The gas sensing properties of PS/WO3 nanowires were investigated toward NO2 gas of 0.5-2 ppm at 25 degrees C up to 125 degrees C. The composite exhibited an anomalistic p-type semiconductor behavior due to the strong effect of the heterojunction. In addition, the composite showed an excellent response, great selectivity and stability for efficient detection of ppm even ppb level NO2 at 25 degrees C. We proposed a qualitative explanation to discuss the gas sensing mechanism. These results were significant from the standpoint of applications requiring great room temperature gas sensing. (C) 2016 Published by Elsevier Ltd.