Based on laser-induced incandescence (LII) and cavity ring-down spectroscopy (CRDS), we establish a measurement setup for the study of flame soot particles, and characterize the performance parameters. The measurement results of the path-integrated attenuation coefficient of soot particles show that the two-color LII test system and the CRDS system are independent of each other. When the two-color LII and CRDS systems are opened at the same time, the measured path-integrated attenuation coefficient increases first and then decreases with the increase of the height above the burner, and the measurement results of the two systems have good correlation. By optimizing the fitting model and removing the system noise, we obtain a better cavity ring-down signal fitting results.