In this paper, triclinic WO3 nanoplates with prominent cyclohexene sensing and photocatalytic properties were fabricated via a facile hydrothermal method assisted with p-aminobenzoic acid. The as-prepared product was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD, SEM and TEM images illustrated that the WO3 nanoplates have a triclinic phase with the length of 100–200 nm and the thickness of 50–80 nm. The gas sensing properties of the WO3 nanoplates were measured by detection of methanol, ethanol, cyclohexane, benzene, ethyl acetate and acetone at 160–300 °C, and their photocatalytic activities were investigated by the degradation of methyl blue (MB). The as-prepared product exhibited not only excellent photocatalytic property for the degradation of MB, but also high response (1000 ppm of cyclohexene, Ra/Rg = 140) and excellent selectivity for the detection of cyclohexene.