Consideration is given to an experimental study of the dynamics of the plasma formation of inert gases (Ar, He) of a pulse-periodic resonant microwave discharge in the pressure range 1×10 -3 -10 Torr and the supplied HF-power up to 600 W. It was shown that the integral intensity of optical radiation increases with the increase of the HF-power absorbed in the discharge. The time dependences of incident and reflected power, as well as the integral intensity of optical radiation in the phase of breakdown and plasma build up time of a stationary state were measured. The dependences of the typical times of the plasma formation from the operating parameters of the discharge (pressure of plasma gas, input HF-power and the duty cycle of heating) have been obtained. © 2018 Federal Informational-Analytical Center of the Defense Industry. All rights reserved.