As a new member of ionized physical vapor deposition (I-PVD) family, high power pulsed magnetron sputtering (HPPMS/HiPIMS) technology has drawn much attention from experts at home and abroad after being discovered due to highelectron density and metal ionization rate. Ionization mechanism and definition of ionization rate of the technology were summarized from the perspective of metal ionization rate in the process of high power pulsed magnetron sputtering. On this basis, measuring methods of ionization rate which were commonly used in recent years were reviewed, including plasma emission spectrometry, atomic absorption spectrometry, mass spectrometry, multi-gridquartz crystal microbalance, and deposition with positive bias voltage. Advantages and disadvantages of each method were compared. Furthermore, key factors affecting ionization rate were summarized, such aselectrical parameters including target power, pulse width, frequency, duty cycle and peak current, as well as non-electrical parameters including target materials, gas pressure and magnetic field. Finally, the effects of ionization rate on properties of films were reviewed. The effects of ionization rate on microstructure, oblique incidence deposition and homogeneity of the filmswere discussed in detail. The work aims to provide reference for better controllingand optimizing ion characteristics during sputtering and theoretical basis for preparing high-quality films.