Bauxite exploration in Xiaolongmiao mining area, Mianchi County, Henan Province is one of the large-scale bauxite exploration projects completed by our company. The lithology of strata in mining area is complex, and there are many mined-out areas. In the process of exploration and construction, the company took the lead in adopting hydraulic thin-walled drilling tool rope coring technology in China, which has small construction area, convenient relocation and high core recovery rate. Combined with drilling work, transient electromagnetic method (TEM) is used to comprehensively explore mined-out areas, which can intuitively and accurately reflect the distribution of underground mined-out areas and provide more accurate guidance for future mining work. This project won the third prize of non-ferrous metal geological prospecting achievements of China Nonferrous Metals Industry Association in 2020.