Biological electrical impedance is a physical quantity to reflect electricity character of biological tissue, apparatus, cell or whole organism, which is a kind of new method developed recently to analyze component of body. This technology is unhurt examining method which obtains certain biomedicine information about human body according to electrical character and change of biological tissue or apparatus, has unhurt, cheap, safe, innocuity, operator simple and abundant information etc., is prone to be accepted by doctors and patients. Now unhurt brain electrical impedance double channel examining system and brain electrical impedance topographic mapping system have entered clinical experiment moment, and contactless magnetic induction tomography(CMIT) is taken notice of widely as a more effective examining method.