Abstract: Although the technique for extracting altered mineral information using near-infrared bands of multispectral remote sensing images is very developed, how to use thermal infrared bands to quantitatively identify the basic-ultrabasic rocks that are closely related to magmatic liquation deposits needs to be explored. By analyzing the emission spectrum characteristics of typical minerals in the range of thermal infrared spectrum, a "basic degree index method" was proposed. The Liuyuan area of Beishan was selected as the experimental area, and basic-ultrabasic rocks were identified based on ASTER thermal infrared data, and the effectiveness of the method was quantitatively evaluated by means of indoor comparison and field verification. The results show that the new method can identify basic-ultrabasic rocks well, the overall identification accuracy can reach about 70%, and the boundaries of the identified rock masses are more detailed than those mapped in the previous geological maps. The application analysis of the Hongliugou typical area shows that the distribution characteristics of the basic-ultrabasic rock masses identified by remote sensing are consistent with the actual geological conditions, and the high-basic degree index area overlaps with the known geomagnetic and geochemical anomalies very well. These findings provide a new basis for the use of multiple methods to locate basic-ultrabasic rocks in mineral exploration. The research results have theoretical and practical significance for similar research in Beishan and even Northwest China.