Abstract: The method of surface high-precision magnetic measurement is broadly applied in the present 1:50000 mineral resources survey. The magnetic measurement data should be fully used to obtain ore-searching information. Magmatic activities and structural movements are key factors for the forming and emplacing of mineral resources. The main objects of the study of magnetic measurement data are just the hidden rock bodies and structures. The occurrences and shapes of hidden rock bodies can be effectively inferred by analysis and comparison of magnetic field and anomaly characters, combined with geologic data to tell the causes of the anomalies and verified by other methods. The inference of hidden rock bodies is significantly important for research of intrusive rocks, ore-controlling structures and hidden ore bodies related to magmatic hydrothermal fluid.