This paper introduces the transport network optimization requirements and analyses problems existing in optimization on the basis of clear optical fiber based network architecture and construction standards in order to enhance the effect of the transport network optimization in large and medium size cities. This paper also discusses and compares the choice between "macroscopic" and "microcosmic" based on the needs and problems above. Here

the idea of optimization based on microgrid is formed. Specifi c evaluation and calculation method is proposed by setting up a health index system. Finally this paper gives the guidance of optimization of transmission network based on microgrid in large and medium cities.