Abstract: The volt-ampere characteristics deciding the electric arc power, which affect the fusion of the spraying powder and then influence the quality of coatings, are affected by many factors including gas species, gas flow rates, the nozzle's aperture and compression angle.So the factors influencing the volt-ampere characteristics were studied.The results showed that the arc voltage is increased with the primary gas flow rates in some range.The secondary gas flow rates have 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.