The plasma torch is one of the most important equipment during air plasma spraying, is used to produce the plasma arc in the nozzle for the acceleration and heating of particles. The voltage-current characteristic of the plasma arc is very important to the fusion of particles. The volt-ampere characteristic is affected by many factors, such as gas species, gas flow rate, nozzle geometry and the type of gas injection. So the factors influencing the voltage-current characteristics in high velocity plasma spraying were studied. As the results showed, the arc voltage is increased with the increase of the primary gas flow rate in some range. The secondary gas flow rate has an important effect on the electric arc voltage. The influence of nitrogen on the arc voltage is more than argon when they are chose as the primary gas in plasma spraying. The arc voltage is decreased with the increase of the nozzle’s compression angle and the decrease of the nozzle’s aperture, when the length of the nozzle is unvarying.