The invention discloses an injection current thermo-acoustic resistivity image reconstruction method based on an optimized iteration method. According to the method, current is injected into an imaging target body through an electrode, joule heat is generated in the imaging target body, heat expansion is generated, injection current thermo-acoustic signals are generated, various fault thermo-acoustic signals of the target body are acquired by the aid of an ultrasonic transducer, thermo-acoustic source distribution on each fault of the target body is acquired according to an injection current thermo-acoustic pressure fluctuation equation, integral thermo-acoustic source distribution of the target body is acquired by an interpolation method, spatial dispersion of the resistivity of a conductive object is performed, an initial value of the resistivity is set, electric vector potential of the target body is reconstructed by the aid of a linear finite element equation according to an ohm law, an equation about a thermo-acoustic source and the electric vector potential meeting the resistivity is acquired by a current continuity theorem according to a relationship between the thermo-acoustic source and current density, a target function is defined, the solved electric vector potential is substituted into the target function, and the resistivity of the conductive object is solved by the aid of the minimization principle of the target function.