The national unified power market system based on the inter-provincial and intra-provincial two-level market framework is an inevitable trend of market development. At this stage, the connecting mode of inter-provincial and intra-provincial market two-level declaration, layered clearing and border locking undoubtedly increases the difficulty of market participation and hinders the pace of further deep coupling of the two-levels market. Therefore, this paper comprehensively considers the operation characteristics and bidding factors of power generators with different power supply structures and power purchasers with different load structures, and puts forward a unified step quotation method. Considering the different clearing modes of “physical contract” inter-provincial market and “financial contract” intra-provincial market, a two-level market hierarchical optimization and coupled iterative clearing mode is proposed. Finally, on the premise of "daily clearing and monthly settlement", the flow of settlement information between the trading department and the settlement department at all levels and the flow of funds between market players and power grid companies at all levels are sorted out.