Abstract: The infrared radiation variation of the 2015 Nepal M_S8.1 earthquake were analyzed by using improved robust estimator of thermal infrared radiation anomalies (RETIRA) method based on NOAA outgoing longwave radiation (OLR) daily data from January 2007 to August 2015. The results show that the significant OLR anomalies over the earthquake rupture surface only appeared half a year before the event in long-term scale (3158 days). And the study on the Himalayan tectonic segmentation in this paper shows that the OLR anomalies appeared to the west of the epicentral area, revealing that the stress concentration on the west side of Himalayan tectonic zone is higher than that of the east during the seismogenic process, which is consistent with the stress variation characteristic based on GPS observation by other researches. The spatial distribution of OLR anomalies were mainly concentrated on the southern Himalayan tectonic zone, which is in agreement with the compressional zone in the southern region and the extensional zone in the northern region of the seismogenic obtained from the focal mechanism. Considering the spatio-temporal characteristics of OLR anomaly variation, the anomalies detected in this study were considered to be related with the Nepal M_S8.1 earthquake.