Lightning surge intrudes substation along transmission line to endanger the equipments in a substation.Lightning overvoltage is generated by backflash and shielding failure on the overhead line.In this paper

the overvohage of 750 kV AIS substation caused hy lightning intruding wave is investigated

and the resulting overvoltage magnitudes at several basic points in the substation（including input line

bus bar and power transformer）are computed.A simulation model is established considering the electric equipments

transmission line

steel tower

inner connecting line

and bus bar together as a network.The lightning intruding overvoltage of different running modes and configuration schemes of MOA are calculated by using EMTP （electro-magnetic transient program）

and an optimal MOA configuration is presented.The result shows that lightning protection of substation can be improved by introducing MOA and optimizing its configuration based on accurate overvohage analysis.