By utilizing data from the absolute geomagnetic charts (197l, 1980) com-piled by Institute of Geophysics,Academia Sinica, the principle of sphericalharmonic analysis was adopted to extract regional field, and the principle offrequency spherical analysis was employed to evaluate the depth of Curie sur-fuce. In this way, data-processing was made for geomagnetic fields in the250, 000 km² sharply curved area of the Yarlung Zangbo River. In combinationwith the geologic, geothermal and seismic data of this area, the variations ingeomagntic fields and magnetic basement were analysed comprehensively, andthe locations, strikes and dips of the tectonic lines of deep faults in this areadeduced. All these results provide reference information for the knowledge ofgeoiogic conditions at depth of this area.