The basic requirement of the 5th Generation (5G) network is to realize automatic end-to-end service arrangement and slice orchestration. In this paper, considering the purpose of the open standardization of the Northbound Interface (NBI) of 5G transport network, we first analyze the functional requirements of the NBI. Then the modeling scheme of the NBI is proposed. Finally, the different technical implementation schemes of 5G transport network are shielded, which provides a reference for the unification of the NBI.