We investigate the key techniques in ammonia (NH₃) measurement based on midinfrared quantum cascade laser absorption spectroscopy technology. As the detection object, the system chose two absorption peaks splitting near 1122.16 cm ^{− 1} at 0.3 atm. It was also combined with wavelength modulation spectroscopy technology and a high-temperature environment to reduce NH₃ absorption in dynamic measurement. Allan variance was used to analyze the stability of the system. The optimal time to measure the average was 195 s, and the minimum detection limit was 121.58 ppb.