Abstract: Objective In order to improve the detection accuracy of TEM,it has been put forward to that the geo-electrical interface underground can be imaged by reflection coefficient. The mathematical model and process step have been provided. Materials and Methods The reflection coefficients are gotten from the data observed in field has been given as follows: Beginning with the data observed in field,calculating wave-impedance with the technical of digital filter in frequency domain, after domain transform functions that contain reflection coefficient have been constructed in time domain. Result At last reflection coefficient has been computed by linear programming。Imaging section of the parameter has been drawn. of numerical modeling and example application show that the thought is right and efficient. Conclusion The method improves the distinguishing capacity of TEM to geo-electrical layer.