Abstract: As a new gas concentration measurement technology, tunable diode laser absorption spectroscopy (TDLAS) is widely used in the field of NH₃ concentration measurement. Using Matlab visual modeling and simulation software Simulink to realize the direct absorption measurement process simulation of NH₃ concentration TDLAS with mid-and-far infrared quantum cascade laser (QCL) and near-infrared distributed feedback laser (DFB) as light source, under the environmental parameters of flue gas denitration and normal temperature and pressure respectively, the sensitivity, detection limit and resolution of NH₃ concentration measurement were theoretically analyzed. The results show that theoretical sensitivity of the QCL-TDLAS system is about 50 times higher, compared with the traditional near-infrared DFB source. The detection limit and resolution can reach the ppb level, and the trace NH₃ concentration measurement capability is greatly improved. The simulation process and results provide theoretical basis for QCL-TDLAS technology in NH₃ concentration measurement.