Pseudo-spark switch(PSS) is one of the most widely used discharge switches for pulse power technology.It has many special characteristics such as reliability in a wide voltage range,small delay time,as well as small delay jitter.In this paper,the measuring method for the initial plasma of ZnO surface flashover triggering device of PSS is studied and the results of the measurement show that the electron emission charge is mainly influenced by trigger voltage,gas pressure and DC bias voltage.When the bias voltage increases from 2 kV to 6 kV with the gap distancc fixed at 3 mm,the electron emission charge changes from 2 μC to about 6μC.When the gap distance changes from 3 mm to 5 mm with the bias voltage fixed at 2 kV,the electron emission charge increases from 1.5 μC to 2.5μC.When the gap distance is 4 mm,the hold-off voltage of PSS is 45 kV at gas pressure of 2 Pa,the minimum operating voltage is less than 1 kV.So,the operating scope is from 2.22%to 99%of its self-breakdown voltage.The discharging delay time decreases from 450 ns to 150 ns when the trigger pulse voltage is 1 kV and the discharging voltage is changed from 1 kV to 12 kV.When the trigger pulse voltage is 6 kV,the discharging delay time is less than 100 ns and changes from 100 ns to 50 ns,and the delay jitters are less than30 ns. Pseudo-spark switch (PSS) is one of the most widely used discharge switches for pulse power technology. It has many special characteristics such as reliability in a wide voltage range, small delay time, as well as small delay jitter. In this paper, the measuring method for the initial plasma of ZnO surface flashover triggering device of PSS is studied and the results of the measurement show that the electron emission charge is primarily influenced by trigger voltage, gas pressure and DC bias voltage. kV to 6 kV with the gap distancc fixed at 3 mm, the electron emission charge changes from 2 μC to about 6 μC. What the gap distance changes from 3 mm to 5 mm with the bias voltage fixed at 2 kV, the electron emission charge increases from 1.5 μC to 2.5 μC .When the gap distance is 4 mm, the hold-off voltage of PSS is 45 kV at gas pressure of 2 Pa, the minimum operating voltage is less than 1 kV.So, the operating scope is from 2.22 % to 99% of its self-breakdown voltage. The discharge delay time decreases from 450 ns to 150 ns when the trigger pulse voltage is 1 kV and the discharging voltage is changed from 1 kV to 12 kV. The trigger pulse voltage is 6 kV, the discharging delay time is less than 100 ns and changes from 100 ns to 50 ns, and the delay jitters are less than 30 ns.