The present invention provides a non-contact impedance sensor which is mounted on measuring region, the radial section structure of the sensor comprises of four layers, metal tube layer, insulation material layer, electrode array layer and insulation ring layer from outside to inside in turn. At least two electrodes are distributed in one circle on the insulation ring layer whose thickness is less than 1% of external diameter, and electric field intensity between electrode array and metal tube layer is less than breakdown strength of insulation layer. The electrode array is separated with measuring region by insulation ring layer. Two image reconstruction algorithms to realize electrical impedance tomography based on the said sensor are also provided. The present invention provides analytical medel, corresponding sensitivity distribution expression and two rapid imaging methods, the sensor can measuring synchronous same-positional dual-mode impedance, advance mutual fusion of real parts and imaginary part information of impedance distribution, predigest the design and implement of software and hardware of dual-mode measuring system.