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Plasma j et is a new type of rapid and wide—frequency aerodynamic actuator,which can significantly improve the aerodynamic characteristics of aircraft and power plant.Spark discharge plasma jet is advantageous for developing the higher pressures and jet velocities,compared to dielectric barrier discharge plasma actuator,which is very useful for supersonic flow contr01.In this paper,spark discharge plasma jet driven by nanosecond high voltage pulses is studied experimentally under varying voltages,frequencies.The rotational temperature of N2(C3Hu)molecule is calculated according to its rotational emission band near 3 80.5 am.The average electron energy of the discharge is evaluated by emission intensity ratio of first negative system(391.4nm)to second positive system(3 80.5nm)of N2.As the voltage increases,both the N2(C3Ⅱu) rotational temperature and the j et velocity increase,while emission intensity ratio of 39 1.4nm to 3 80.5nm remains unchanged.As the frequency increases,the jet velocity increases,while both the N2(C3Hu)rotational temperature and emission intensity ratio of 391.4nm to 380.5nm remain unchanged.The jet pressure is measured using a high frequency pressure transducer.A theoretical estimate of the j et velocity can be obtained by the model of isovolumetric process.