Soot particles from the combustion of hydrocarbon fuels are the main source of the air fine particles and they are also an important factor of reducing the combustion efficiency. As one of their major precursor, acetylene (C ₂H ₂) plays an important role in forming soot. So the simultaneous detecting of soot particle and C ₂H ₂is significant in studying the mechanism of the soot formation. In this work, a sensor for the simultaneous detecting of soot particle and C ₂H ₂is developed by using a single DFB diode laser with a wavelength near 1540 nm. The extinction spectrum near the proper C ₂H ₂line at 6490.02 cm ^–1is used to infer the mass concentration of particles and the C ₂H ₂concentration. The performance of the sensor is confirmed in a home-made heated static cell which can provide well controlled gaseous environment and particulate environment. The measured mass concentration of particles and the C ₂H ₂concentration are within 2.73% and 5.17% of the expected values over the full temperature range of 500–1000 K, respectively. All the measurements show the potential application of the sensor in the simultaneous detecting of soot particle and C ₂H ₂at elevated temperature.