Financial mechanism of the UNFCCC represents the link to connect the global action in tackling climate change, as well as the key element to achieve '2℃ even 1.5℃ goal' through international cooperation. Over the years, due to the fundamental divergence over whether or not to divide the climate obligation based on historical responsibility between the developed and developing countries, the financial mechanism of UNFCCC faces a series of questions, such as paralleled multi-channels,diversity of operational rules, dispersity of finance usage, low operational efficiency and the lack of performance evaluation system. This study summarizes the foundation and operation of each financial mechanism under UNFCCC,analyzes the defects and challenges of these mechanisms in the global climate financing architecture, and establishes the financial mechanism in a whole manner based on the text description and obligation specified in the finance section of Paris Agreement. At the level of institutional building, funding apportionment mechanism and centralized management platform under UNFCCC need to be in place to ensure the adequacy,predictability of climate finance and its responsiveness to the Convention. At the operational level, the optimizing of financial distribution among different channels and recipients will promote the fairness and efficiency of climate finance. At the using level,a unified national entity to manage the finance and the corresponding monitoring and evaluation system should be established to improve the country ownership and environmental benefits. Financial mechanism of the UNFCCC remains the main channel for international cooperation to deal with climate change in the future. Under the adoption of Paris Agreement, the formal operation of Green Climate Fund and the establishment of new international climate regime, how to utilize the financial mechanism to promote the developed countries to fulfill their obligations under the UNFCCC,provide the financial,technical and capacity building support to developing countries is of important practical significance to realize the integrity and balance of each element of the Convention,to promote the global action in tackling climate change,as well as to consolidate the position of developing countries in climate change negotiation.