Abstract: As the penetration rate of renewable energy in the power system continues to increase, the operation flexibility of the power system is facing new challenges. The flexible regulation potential of the power system must be fully tapped to further promote the consumption of renewable energy. For this reason, the United States has introduced flexible ramping product (FRP), a new type of auxiliary service in the electricity market, to deal with the lack of flexibility in the short term. China is in a critical period of electricity market reform, a reasonable market mechanism is of great significance to ensure the flexible operation of the power system. This paper first summarizes the definition and connotation of power system flexibility, and the approaches of improving power system flexibility. Then, FRP is compared with traditional ancillary services, and research on optimization models and market mechanisms considering FRP are summarized. In addition, two market clearing models considering FRP based on deterministic and robust optimization model are given. Finally, the issues and research topics that need to be solved in the future FRP research are prospected, and suggestions and reflections about the market mechanism of improving the flexibility of power system in China are put forward, to provide certain guidance and suggestions for the safe, economic and flexible operation of the system with high penetration of renewable energy resources.