The development process of China's electricity market based on large-scale direct electricity purchase between generation enterprises and large customers is reviewed，and the significance of direct electricity purchase for sustainable development of China's electricity industry and optimal resource allocation is analyzed. Moreover，the impact of direct electricity purchase on the existing power dispatch mode is revealed，and the main principles for the institution design of direct electricity purchase are proposed. On the above basis，an innovative design for direct electricity purchase is proposed，including market entry rules，trade mode，trade category，contract delivery，transmission pricing，market systems，etc. Also included is an incentive mechanism for cultivating the market，a trade mode considering the non-market property right system in China，a secondary direct electricity purchase market，a transmission and distribution pricing mechanism beneficial to power system security，a financial contract delivery method and some supporting measures for direct electricity purchase.