Abstract: With the increase of non-synchronous generators such as renewable energy and high voltage direct current transmission system, the inertia of power system has been reduced, which in turn leads significant changes to frequency characteristics of power system. Synchronous condensers as one type of synchronous machines has inertial responses, which provides short-time frequency support for the system. Firstly, the principle of inertial response of synchronous condensers and its interaction with synchronous generators are introduced. Secondly, taking the application of inertial response for synchronous condenser as entry point, the worldwide work on improving the inertial responses and frequency characteristics of power system is sorted out, including the synchronous inertia level of power system, the measurements to improve the synchronous inertia, the effect of synchronous inertia on frequency response in power system and so on. Finally, combined with the worldwide research experiences, the necessity for East China Power Grid to apply synchronous condensers to enhance the frequency support of power system is analyzed, and relevant suggestions are put forward.