Under the background of the "Dual Carbon" strategic goal，hydrogen-based reduced iron ore is the key path for the green transformation of the iron and steel industry. In this paper，a set of gas online detection system suitable for high- temperature hydrogen-based reduced iron ore is designed and verified by combining Vaisal thermohygrometer and infrared gas analyzer to meet the requirements of high H₂O content. The test is carried out under the conditions of reduction temperature of 1 173 ~ 1 373 K，reduction atmosphere of 60% CO + 40% H₂ and reduction time of 40 min. The results show that the system has good responsiveness and sensitivity under high temperature conditions after optimizing the system design. With the increase of reduction temperature and time，the overall error of the gas online detection system gradually is decreased，and the difference between the measured results of the weightless loss and breakpoint weighing calculated by the system is 0. 01 ~ 0. 11 g，which is within the range of measurement error and has high accuracy. Based on the designed gas online detection system， it can provide a new detection method for the dynamics study of hydrogen reduction at high temperature in the laboratory.