A rapid method for 3D physical properties inversion based on separation and continuation of potential field are introduced in this paper. The inversion technique characterized by faster computing speed, it does not need to divide the underground field sources region into many rectangular blocks in one time and does not need to solve linear algebraic equations as well. So, this technique can overcome the requirement of large computer memory, unstable solution and computation time bottleneck which hinders the application of 3D inversion to practice. The method is used to apparent magnetic susceptibility inversion of magnetic anomaly in a iron mine area, the inversion results show that the method has good accuracy, and the advantages of strong stability and a high computation speed, and is suitable for 3D inversion of magnetic data in large area.