To improve the integration of power grids and public communication networks, this paper proposes a novel delay-optimized placement method for the Service Function Chain (SFC). This is intended to solve the problem of delay deterioration caused by the dynamics of network connection selection and the difference in segmentation schemes of SFC in a network convergence scenario. First, by proposing an integration model of power grids and public communication networks, this method describes the SFC placement problem as a Binary Integer Programming (BIP) problem whose objective function is the minimum of SFC’ delay. Then, it searches the optimal network connection and SFC segmentation scheme using the minimum spanning tree algorithm, and that splits the SFC placement problem into two homogeneous problems of sub-chain placement. Finally, a nested sub-chain placement method based on minimum spanning tree is proposed to obtain the delay-optimized placement scheme for two sub-chains placed on a power communication network and public communication network respectively. Simulation results show that, compared with existing SFC placement methods, the proposed method improves the total delay by 29.34% and the acceptance rate of SFC service request by 12.08% on average. This work is supported by the National Natural Science Foundation of China (No. 51777068) and the Science and Technology Project of State Grid Corporation of China (No. SGTYHT/19-JS-215).