The test technology of extinguishing agent concentration based on pressure difference mechanism is the key technology for the effectiveness test of fire extinguishing system design in engine compartment, APU compartment and front and rear cargo compartment of civil aircraft, and is also a widely recognized method for measuring extinguishing agent concentration in the world. At present, most of the equipment related to the concentration measurement of fire extinguishing agent in China comes from abroad, and the relevant research situation is relatively weak due to this constraint. Based on the measurement technology of fire extinguishing agent concentration by pressure difference method, this paper designs a set of fire extinguishing agent concentration measurement system, which is used to measure the concentration of fire extinguishing agent in the engine room and other areas, and puts forward the key technologies and solutions in the design process of fire extinguishing agent concentration. Finally, the calibration test of the extinguishing agent concentration measurement system was carried out in the laboratory, and the measured data were obtained when the volume concentration of the standard extinguishing agent was 3%, 6%, 10% and 20%, respectively. The measurement error value was less than 0.25%. In addition, the synchronization test of the extinguishing agent concentration measurement system was carried out in the laboratory. By setting different length and bending state of the sample tube, the maximum time difference of the synchronization test of the extinguishing agent concentration measurement system was obtained in different test configurations. The test results show that the maximum time difference of the synchronization test of all channels in the extinguishing agent concentration measurement system is less than 100 ms, and the length and bending degree of the pipeline have little influence on the synchronization of the system described in this paper.