Abstract: Under the background of "carbon peaking and carbon neutrality", the rapid development of renewable energy resources will further change the power supply structure. However, the randomness and volatility of renewable energy outputs bring severe challenges to capacity adequacy. Recent studies have been carried out on capacity adequacy mechanisms, but the effects of different adequacy mechanisms on guiding optimal capacity have not been quantitatively evaluated. This paper selected three capacity adequacy mechanisms: scarcity pricing, traditional capacity auction, and capacity auction with reliability options, explored the equivalence of these three mechanisms in inducing optimal capacity under certainty and the impact on supplier revenues considering the uncertainty of outage hours and generation outputs. Finally, suggestions and concerns were put forward to select capacity adequacy mechanisms in China's electricity market.