Abstract: In the process of clean and low-carbon energy transformation, an increasing share of inverter-based resources (IBRs), especially wind and solar generation, have been integrated into power system. The virtual inertia of IBRs and traditional rotational inertia constitute the generalized inertia, which significantly changes the dynamic characteristics of the active power. Mastering the inertia characteristics and optimizing inertia are important issues concerning the security and stability of future power system. This paper reviews the generalized inertia of new power systems. The definition and mathematical formula of generalized inertia of new power systems are firstly discussed from the universal concept of inertia and relevant factors, then three key issues of heterogeneous inertia quantitative characterization, inertia estimation and optimization considering inertia adequacy are detailedly reviewed. The main research progress, problems to be solved and possible solutions in related fields are explained at length respectively.