Abstract: Preliminary experimental investigation on Magnetohydrodynamic (MHD) acceleration using seeded supersonic flow as working fluid was presented in the paper. Helium and argon were used as driver and driven gas, respectively, in a shock tunnel. Equilibrium contact surface operating mode was used for obtaining high temperature gas. The conductivity was obtained by adding seed K₂CO₃ powders into the driven section, and big capacitor was used for providing electric energy. Voltage and current characteristics, conductivity, load factor, electric efficiency and acceleration effect were measured or calculated on typical experimental condition when the nozzle entry total pressure is 0.7049MPa, theoretical equilibrium temperature of 8372.8K, nozzle outlet Mach number of 1.5, capacitance voltage of 400V, and magnetic field strength of 0.5T. The main results are as follows: the conductivity of supersonic flow is about 150S/m under the existence of magnetic field; the load factor of the MHD acceleration channel is about 4; electrical efficiency is about 28%, and average input power is 198kW; flow velocity was increased by 15.7% by means of electrical parameter measurement, and the conductivity of the supersonic flow has important influence on the electrical efficiency and acceleration effect.