The present paper has dealt with the effectiveness of the second round development and study of aeromagnetic data in the performance of ore prospecting work in Sanjiang region,Southwest China.Based on the theore tical analysis of magnetic anomalies over the Yulong copper deposit and the establishment of a magnetic model for the ore deposit,the authors probe into the effectiveness of applying aeromagnetic data to the prospecting for prophyry type copper deposits.Finally,quantitative analytical technique is employed to make comprehensive information ore prospecting prognosis,with aeromagnetic and remote sensing information playing the dominant role.