Abstract: Insufficient unforced capacity of the system at peak periods with high proportion of renewable energy will affect the safety of system operation, so during the energy transformation, we should fully tap the ability of flexible resources such as renewable energy and demand response to provide unforced capacity at peak periods. Based on the mechanism designs of the US and the UK capacity markets, this paper reviews the renewable energy and demand response resources participating in the capacity markets and the calculation methods of unforced capacity. Finally, combined with the development of the Chinese market, an in-depth thinking about the construction of China's capacity market has been carried out, including steadily advancing the construction of capacity market, designing the capacity market mechanism with high proportion of renewable energy, and constructing a coordinated capacity mechanism across the country.