Magneto-thermo-acoustic imaging uses biological tissues to generate ultrasound signals by excitation of thermal expansion under the pulsed magnetic field, and the conductivity distribution is reconstructed by the ultrasound signals. Magneto-thermo-acoustic imaging combines the advantages of high contrast in electrical impedance imaging and high resolution in ultrasound imaging, but it is still necessary to carry out related research work on complex targets and low-conductivity targets. In this paper, magneto-thermo-acoustic imaging for multi-target under pulsed magnetic field excitation is investigated, and the effects of different conductivities on the imaging results are discussed. A two-dimensional imaging simulation model is established to simulate elliptical and rectangular target bodies, and the effects of different conductivity targets on the acoustic pressure signal are analyzed. The results show that magneto-thermo-acoustic imaging can reflect the boundaries of multi-target bodies, and the change of conductivity affects the contrast and brightness of imaging. The feasibility of multi-target imaging is further verified through experimental studies, and the lower limit value of detectable conductivity is optimized. The theoretical, simulation analysis and experimental results show that the magneto-thermo-acoustic imaging method has great potential in biomedical imaging.