High power pulse magnetron sputtering (HiPIMS) has become a hot spot in the field of PVD due to its high ionization rate of target atoms and excellent film forming property. Macroscopic expression of high ionization rate of target atoms is large discharge current. The work aims to introduce structure and forming principle of plasma discharge target current, analyze the influences of magnetic field, target voltage and working pressure on atomic ionization rate of target material during HiPIMS discharge, and investigate corresponding discharge target current curve. Space magnetic fields could bind electrons and increase trajectory of electrons in front of the target. Increasing magnetic fields or working pressure could reduce mean free path of particle motion, further increase probability of particle collision and atomic ionization rate, and hence increase discharge target current. Increasing the target voltage could increase ion collision energy. The higher the target voltage was, the greater the discharge target current was. The discharge target current curves of various materials at different voltage were analyzed. The excellent film forming property benefitted from good control of ionic motion. The work described a series of microscopic mechanisms including spatial charge distribution of plasma, target self-sputtering and “gas cycle” process, mechanism of secondary electron emission and its ionization promotion, phenomenon of gas rarefaction caused by plasma collision, and Joule heating effect of presheath on secondary electrons and plasma electrons. The contribution of these microscopic mechanisms to ionization of particles was discussed. Finally, potential research direction of HiPIMS plasma discharge was prospected.