Ethernet passive optical network is a new optical access network technology characterized by low cost, high bandwidth, little electromagnetic interference, strong scalability, and powerful compatibility. The auxiliary control system of smart substation includes video surveillance system that carries large data volume but raises low real-time requirement. Constructing the auxiliary control system in the station with Ethernet passive optical network can effectively solve the problem of export bandwidth allocation without using a switch, thus greatly saving the investment in network construction and the costs for life-cycle maintenance. It is therefore regarded as an efficient new networking scheme for the auxiliary control system of smart substation. This paper analyzes the feasibility of applying Ethernet passive optical network technology in the auxiliary control system of smart substation, proposes a program to construct a 220kV smart substation using Ethernet passive optical network, and conducts an economic comparison, in an attempt to provide a new solution for the data transmission of the auxiliary control system of smart substation.