Introduce the theory and application of the Impedance Method and set up the model of fictitious human. After dividing the human head into many cube griddings, every gridding edge could be thought of the impedance based on the head. The current in one section of the loop could be confirmed by the line impedance, which based on the permittivity and electric characters of the matter which is covered by the gridding. Using C++ computing and picturing the datum by Matlab, 3-Dimension SAR of each lay would be found. After comparing with the results of FDTD, the Impedance Method is more easy, more perspicuity, more quick and don’t need consider the strict boundary.