The invention provides a method for econstructing specific conductivity of thermoacoustic tomography based on the principle of current injection thermoacoustic tomography. A pulse current is injected into an imaging object via an electrode to generate joule heat in the imaging object, which then induces thermal expansion and generates an ultrasonic signal, the ultrasonic signal is received by an ultrasonic transducer and then processed and collected, and the specific conductivity images of the object is obtained by a specific conductivity image reconstruction algorithm. The specific steps are as follows: (1) obtaining a current injection type thermoacoustic signal; (2) reconstructing a thermoacoustic source of the object by using the obtained current injection type thermoacoustic signal; (3) reconstructing an electric scalar potential from the thermoacoustic source by a nonlinear finite element solution method; and (4) reconstructing specific conductivity by using the reconstructed electric scalar potential.