The 5G bearer network consists of three parts: pre-transmission, intermediate transmission, and backhaul transmission. The integrated service access node bearer devices can aggregate the pre-transmitted traffic to the wireless devices of the node, and can also upload the intermediate/backhaul services to the upper-layer bearer devices. The integrated service access node requires a rich access service types and high requirements for bandwidth and delay. Packet enhanced OTN (POTN) can well meet above requirements. IP Radio Access Network (IPRAN) has been widely used in 4G bearer network. In order to achieve intelligent upgrade of the network, the POTN+IPRAN scheme came into being. For each operator, it is necessary to reduce the construction cost of the bearer network while meeting the needs of new services and new scenarios in the future. In this paper, we design a cost-minimized algorithm for POTN device in POTN+IPRAN 5G bearer network (CM_POTN). We set two constraints, they are the number of centralized BBUs on each integrated service access node and the number of integrated service access nodes on each integrated service access ring. For the purpose of minimizing the cost of POTN devices, the algorithm attempts to calculate the minimum cost of the main component modules in the POTN devices within the two constraints. Moreover, a simulation is designed to evaluate the performance of the proposed algorithm, and results show that our proposed CM_POTN algorithm can achieve the minimum cost of the POTN devices within the given constraints.