Abstract: This article focused on the optimization problem of maintenance scheme of EMU under networked operation and maintenance condition, took the output data of EMU in fixed operation mode as output, met the maximum number of repairs in EMU depot, EMU one or two level maintenance procedures and multiple maintenance of resource sharing rules as constraints, aimed at minimizing the remaining capacity of EMU maintenance, constructed the optimization model. The article designed solution strategy of the model based on ant colony optimization algorithm, implemented maintenance resource sharing among EMU depots, made full use of the maintenance cycle of EMU, reduced maintenance cost.