In order to assist Parties in achieving their mitigation targets under nationally determined contribution （NDC） and incentivize them to increase mitigation ambitions，Article 6 of the Paris Agreement establishes two market-based mechanisms，i.e. cooperative approaches and sustainable development mechanism. Influenced by the diversity of NDC mitigation targets and the uncertainty of future mitigation efforts，global carbon market mechanisms are facing enormous risks and challenges in their design and implementation. In this paper，key elements that may lead to great risks in the design of market mechanism are identified and analyzed. Then the sources and potential impact of risks are deeply analyzed from the perspectives of ensuring robust accounting，improving additionality assessment of emission reduction activities and promoting Parties’ mitigation action. To reduce the negative impact of these risks on global climate action，the paper proposes several suggestions，including establishing a robust accounting system，taking appropriate consideration of NDC commitment in additional assessment，as well as ensuring the promoting role of market mechanism in increasing Parties’ mitigation ambition by different ways，such as establishing participation requirements，etc.