The soil samples uniformly overlying the Bairendaba deposit of the Inner Mongolia grassland were collected, and analyzed with X-ray diffraction (XRD) and near infrared spectrum (NIR), for exploring the origins of the soil from the grassland mining area and the relationship with the underground rock. The results show that the samples consist of quartz, graphite, carbonate, hornblende, mica, chlorite, montmorillonite, illite, berlinite, diaspore, azurite, hematite, etc. These indicate that the soil samples were not only from the weathering products of the surface rock, but also from the underground rock mass and the alteration of the wall rock. The azurite and the hematite contained in the soil, mainly coming from the oxidation zone of the ore-bodies, can be used as the prospecting marks. The alteration mineral assemblage is mainly chlorite-illite-montmorillonite and it experienced the alteration process of potassic alteration→silicification→carbonatization→silk greisenization→clayization. Also, the wall rock alteration and the physical weathering processes can be accurately restored by analyzing the combination of the alteration minerals, which can provide important reference information for the deep ore prospecting and the ore deposit genesis study, improving the rate of the prospecting. The XRD and NIR with the characteristics of the economy and quickness can be used for the identification of mineral composition of soil, and in the study of mineral and mineral deposits. Especially, NIR has its unique superiority, that is, its sample request is low, and it can analyze a batch of samples quickly. With the development of INR, it will be more and more widely applied in geological field, and can play an important role in the ore exploration.