With the continuous advancement and deepening of smart substation construction in State Grid Corporation, according to the guidance of new generation smart substation with "highly integrated system, rational layout, advanced and applicable equipments, energy conservation and environmental protection, and supporting integrated control," the technology of equipment integration and layout optimization was studied, combined with the feature of Dashi 220 kV new generation smart substation. Then, the design principles of primary and secondary equipments of smart substations were explicitly stated, the scheme of equipment selection among disconnecting circuit breaker, gas insulated switchgear, gas insulated busbar, hierarchical protection & control system and container-type equipment was proposed. Finally, the main wiring diagram and optimization design of general layout were presented for Dashi substation, and technological and economic analysis was carried out on the highly integrated equipments in smart substation, which would provide references for similar substation design in future.