To meet the demand for simultaneous real-time monitoring of CO? concentration and gas flow velocity in flue gas streams for industrial emission monitoring, this paper presents a synchronised measurement system based on tunable diode laser absorption spectroscopy (TDLAS). A distributed feedback (DFB) laser with a centre wavelength of 2004?nm was employed as the light source. The system retrieves CO? concentration by exploiting the characteristic absorption lines of CO? molecules in the near-infrared band, and determines the flow velocity using a dual-path compensation algorithm, thereby enabling collaborative sensing of key flow-field parameters. Experiments for simultaneous measurement of CO? concentration and velocity were conducted under various flow-rate conditions in an annular wind tunnel, and the results were verified by comparison with reference instruments. The experimental results show that, under different flow velocities, the velocity measurement deviation ranges from 0.11 to 1.04?m/s, with a maximum measurement variance of 1.27?m/s; for the two independent optical paths, the CO? concentration deviation lies between 0.06?% and 0.09?%, with a maximum variance of 0.06?%. The system operated stably throughout the tests, exhibited good measurement repeatability, and the correlation between concentration and velocity data was consistent with theoretical expectations. The proposed device enables simultaneous on-line monitoring of key flue-gas parameters without disturbing the flow field, providing a reliable technical means for combustion diagnosis and quantitative emission control.