In this paper, a closed-loop feedback control system for the measured ammonia gas pressure is designed based on Bernoulli's principle, and the high-resolution spectral characteristics of NH3 under low pressure conditions are studied. The system takes the measured ammonia absorption tank pressure as the control object, uses CDG800 pressure sensor to measure the absorption tank air pressure, one of the VT317 solenoid valve controls the high pressure standard concentration ammonia source to increase the air pressure in the absorption tank, and the other VT317 solenoid valve controls the vacuum pump extraction The gas in the absorption cell reduces the pressure to form a low-pressure gas circuit for NH3 spectrum detection; and a closed-loop feedback control circuit for pressure measurement, solenoid valve and vacuum pump with Arduino UNO microcontroller as the core is designed. The experimental results show that the designed air pressure control system can maintain a stable time for more than 72 hours, and the air pressure fluctuates within 1 torr. A single absorption spectrum signal in the NH3 mid-infrared band 1103.4cm-1 is obtained, and the calculated line intensity is consistent with the center line of the HITRAN database. The strong data deviation is between 2.71% and 4.71%.