In view of the difficulties in organizing inter-provincial power transactions caused by the low accuracy of renewable energy power generation forecasts, and in conjunction with the requirements of the new version of the trading rules on contract adjustments and deviation assessment, this paper conducts to formulate a flexible mechanism for medium- and long-term contracts, designs a fusing market for electrical energy (primary market) and contract changes (secondary market), in which new energy sources can realize flexible contracting. On the basis of the fusing market, a new energy medium- and long-term flexible contracting process is proposed, including standardization of contract adjustments, data declarations, trading mechanisms, market clearing and settlement, contract changes, contract termination, contract defaults and processing standards.