Abstract: A new method for reconstructing lossy medium by regression circle technique is presented. In high frequency region, the locus of the reflection coefficient as a function of the wave number in the complex plane yields a circle, from which some properties of the medium can be reconstructed without recourse to any numerical techniques. The method not only can be applied to the complex reflection spectrum but also can be adapted to treat the amplitude spectrum alone, therefore it makes the method more practicactical.