Abstract: We study the kinetics of lasing ions and the required electron temperature and density conditions for the lasing plasma media in resonant photo-pumping scheme. The relations between the effective pump photos/mode and gain，inverse factor and decay factor are obtained. Some conditions which the pump radiation source must satisfy are given. As a result of study, the photo-pumping scheme is possible to demonstrate if resonant line pairs are found, while the auto-resonant photo-pumping is difficult. Finally,Z-scaling law is presented.