We investigates the magnetic field intensity effects on the discharge characterization of Hall thrusters for optimization of the magnetic fields by varying the strength of magnetic fields with its topography holds constant （keep in "focusing" type）, and making an experimental study of the thruster's operating performance working in different regions of magneto-ampere curve through Langmuir probe, spectrograph, etc.. The results shows that when the magnitude of magnetic field intensity is less than its optimal value, near-wall conductivity gives priority to the activity that electrons traverse the magnetic field; contrarily, discharge current varying with magnetic field intensity abnormally, and existing electrons conductive theories are failed to explain this phenomenon.