The equivalent &ource method has been extensively used ia the interpretation of satel-lite magnetic anomalies. Ia this paper, however, the equivalent source method is introducedinto the interpretation of the aarbmagnetic AT field to investigate regional tectonics. Based onthe theory of the equivalent source method, we deduced a formula for Ar magnetic field of thelower spherical prism of the spherical coordinate system, and made model test using the linearinversion method. This method was used to make tentative calculation of aeromagnetic T ano-malies in Qinlins-Bashan area and, as a result, reached some valuable conclusions. With thismethod, the Curie depth distribution can be obtained from the calculated magnetic field inten-sity.