An optical method was used to determine the axial velocity of plasma jets produced by a DC plasma spray torch. Different experimental conditions were tested in order to systemically study the influence of the working parameters on the plasma velocity. In this way, the are current ranged between 200 and 600 A, the gas flow rate between 30 and 80 slm, and the internal nozzle diameter between 6 and 10 mm, the plasma gases were either an Ar-H-2 mixture or N-2. Rather well defined tendencies were observed and at the same time it appeared that the are stability greatly influenced the fluctuations of the velocity.