According to the technical standards and requirements on distribution network planning， construction and distribution automation of the smart grid project， the large-scale distribution automation implementation project for metropolises is studied. The details of distribution automation are exhibited with examples， such as multi-specialties， the appropriate technical route， engineering feasibility， technical demand of the distribution network operation and maintenance as well as supporting technology. The important technologies also include network regional feature analysis， the design level of the year， planning principles of project scale， master station and information content planning， scale control， general technical requirements， architecture and functions of the master station， architecture， interaction boundaries and application of the information exchange bus， distribution automation terminal and relevant equipment， design objective and technology of distribution network communication systems， network scheme of Ethernet passive optical network as well as cable design. The thesis displays the basic achievement of the application and proves the correction of the designing thought.