Based on the brightness temperature data obtained from Chinese geostationary meteorological satellite, this paper studied the thermal radiation anomalies before the Menyuan M6.9 earthquake on January 8, 2022 by using the wavelet transform and the relative change of power spectrum, and made a retrospective study on the thermal radiation anomalies of previous earthquakes in the middle-eastern Qilian seismic belt. The development process of thermal radiation anomaly of the Menyuan M6.9 earthquake can be divided into three stages: initial evolution stage, strengthening and persisting stage, weakening and disappearing stage. The largest area of intense radiation was about 80 000 km², and the earthquake occurred in the northwest of the region. The peak value of the relative power spectrum was 17 times the average value, and the M6.9 earthquake occurred 82 days after the peak value. The significant feature of the anomaly is the large area and long duration of high intensity thermal radiation. The characteristics of thermal radiation anomalies before several earthquakes in the middle-eastern Qilian seismic belt can accumulate experience for the judgment of earthquake situation in this area.