In order to improve the path optimization effect and load balancing ability of industrial fiber optic communication network, the routing optimization method of industrial fiber optic communication network under 5G and digital twin is proposed, firstly, the industrial fiber optic communication network is modeled and analyzed with the combination of 5G technology and digital twin technology, and the network state data is obtained; secondly, the minimization of the maximum link utilization rate and the path latency is taken as the objective, and the routing optimization objective function of the industrial fiber optic communication network is established. Finally, the improved sparrow algorithm is used to solve the objective function to realize the optimization of industrial fiber optic communication network routing. The experimental results show that the maximum link utilization of the proposed method is within 20%, the maximum path delay is 0.27 s, and the number of dead nodes is 1/8 of all nodes, which verifies that the proposed method has a good path optimization effect and load balancing capability.