With the advancement of the construction of the national unified electricity market system, the intra-provincial medium and long-term electricity market adopts the trading mode of unrestricted clearance before security assessment, which has been unable to meet the needs of the future medium and long-term market continuous market opening and high-frequency trading requirements. Firstly, this paper establishes a continuous centralized bidding trading mechanism and clearing model for the medium and long-term electricity market. The continuous opening of the medium and long-term market is achieved through daily continuous trading, and the available transmission capacity is considered in the clearing model to improve the enforceability of trading results. Then, based on the marginal clearing price, a Marginal-Vickrey-Clarke-Groves mechanism is established to meet the balance of payments. This mechanism quantifies the contribution of market entities in the transaction through market efficiency coefficient, and distributes the market value. This mechanism can promote the market participants to declare the true price information. Finally, based on medium and long-term & spot electricity market trading data from a certain province in central China, the simulation analysis is carried out on the transaction data including 3 power generation enterprises and 5 power users. The clearing price is 399.64 yuan/MWh, which verifies the effectiveness and feasibility of the mechanism.