MHD acceleration technology is of great hope in application. In this paper, with a MHD experimental system based on shock tunnel being used, the supersonic nozzle and test section (segmented Faraday accelerator) are designed as well as reasonable electric field and magnetic field facilities. Experiments under different magnetic induction are carried out. Under the conditions of 1.1 MPa driver pressure, 500Pa driven pressure and 400 V capacitance voltage, some results are obtained as follows: With the increase of the magnetic field, the voltage at electrode pair #10 rises, while the current is decreased, the input power and the load factor are decreased. When magnetic inductions are differently as 0.5 T, 1 T and 1.5 T, the conductivities of supersonic airflow are about 181 S/m, 81 S/m and 50 S/m respectively, and the increasing rates of outlet speed are estimated to be 16.1%, 14.7% and 14.3% by evaluation method of using open circuit voltage at electrode pair #20. The conductivity of supersonic airflow has an important effect on acceleration, and both the enhancements in electric conductivity and in efficiency are simultaneously needed to improve MHD acceleration.