As a kind of multi-physics imaging approach integrating the advantages of electrical impedance tomography and ultrasound imaging with the improved spatial resolution and image contrast,magneto-acoustic tomography with magnetic induction (MAT-MI) is demonstrated to have the capability of electrical impedance contrast imaging for biological tissues with conductivity differences.By being detected with a strong directional transducer,abrupt pressure change is proved to be generated by the gradient of the induced Lorentz force along the force direction at conductivity boundary.A simplified boundary normal pressure (BNP)-based conductivity reconstruction algorithm is proposed and the formula for conductivity distribution inside the object with the clear physical meaning of pressure derivative,is derived.Numerical simulations of acoustic pressure and conductivity reconstruction are conducted based on a 2-layer eccentric cylindrical phantom model using Hilbert transform.The reconstructed two-dimensional conductivity images accord well with the model,thus successfully making up the deficiency of only imaging conductivity boundary in traditional MAT-MI.The proposed method is also demonstrated to have a spatial resolution of one wavelength.This study provides a new method of reconstructing accurate electrical conductivity and suggests the potential applications of MAT-MI in imaging biological tissues with conductivity difference.