A volatile organic compounds (VOC) sensor built on SOI-based photonic platform is presented in this paper. The sensor consists of a high-Q factor ring-resonator. It is tested with acetone vapor, achieving a detection limit of 200ppm. The sensor obtained relative high sensitivity (1.7 pm/1000ppm), fast response time (∼20 s) and the stability of <1 pm drift, making it suitable for indoor air quality (IAQ) detection and monitoring. Furthermore, by arranging of an on-chip ring-resonator array, the proposed scheme has a potential to detect and distinguish different gas species.