Most of the optimal node selection model in traditional fiber communication of substation is based on prior knowledge. It has low performance and is not suitable for practical application. Therefore, a new optimal node selection model for optical fiber communication of substation is designed. In this model, the structure of fiber optic communication system is given, and the signal receiving and signal transmission in communication process are introduced. Then, the communication links of all photoelectric signals' access terminal and the center are planned as communication grid. Based on the node function, from four aspects, nodes in the fiber optic communication are evaluated, which are communication node processing capability, communication delay between adjacent nodes, channel quality and error rate between adjacent communication nodes. Finally, the weights of the four evaluation indexes are calculated, and the optimum node selection model is designed according to the weights. The results of security and performance testing of the design model show that the model is safe and the whole performance is strong.