Under the background of regional electricity market construction of China， the concept of the interconnection electricity market is proposed; the basic requirements of the interconnection electricity market are analyzed; and various interconnection market models that can realize Pareto improvement are studied. In this paper， the basic model of the interconnection market is established， and the market model that can realize Pareto optimality is analyzed. Furthermore， the fundamental theorem of welfare economics is used to compare and analyze the social welfare of interconnection market model and unified market model. The comparison indicates that the interconnection electricity market and unified electricity market have the same social welfare under the perfect competition assumption， and the interconnection electricity market is a kind of Pareto improvement markets， of which the market players will take the initiative to promote market reform forward. Finally， the path of regional electricity reform from the interconnection market to the unified market is proposed.