Experiments were conducted to investigate the suitability of the multistage in-situ reaction analyzer based on a micro fluidized bed ( MFB-MIRA) for measuring the rapid change of the gas concentration during gas-solid reactions. The results showed that the control performance of capillary temperature had a great impact on the stability of on-line measurement. Based on the observed regular patterns, the capillary temperature control system was equipped with a precision temperature controller. The control precision of capillary temperature reached ± 0 . 2℃, which guaranteed the high stabilities of the sampling flow rate and the chamber vacuum. The measured results of the modified gas monitoring system showed the periodic fluctuations of the on-line measurement were eliminated. The stability of measurement was significantly improved. The fluctuating range and relative standard deviation of the measured response to O2 in air changed from 1. 9% and 0. 5% to 1. 4% and 0. 2%, respectively. A pressure regulating device was also developed to control the absolute pressure at the gas sampling point. The control precision reached ± 0. 02 kPa. The measured results showed that the response of the process mass spectrometer was positively correlated with the absolute pressure at the sampling point, indicating the necessity of the pressure regulating device. The accuracy and repeatability of process mass spectrometer were improved. This study has enhanced the suitability of MFB-MIRA for studying rapid gas-solid reactions and broadened the scope of reliable applications of MFB-MIRA and process mass spectrometer.