Network-on-Chip (NoC) is an emerging technology designed for the communication of IPs in an embedded system. This paper proposes a 3D (Three-Dimensional) model for a Bi-directional NoC (BiNoC). This three-dimensional model inspires the development of a new routing algorithm for BiNoC, called Bidirectional Routing (Bi-Routing). Bi-Routing is a fully adaptive routing algorithm using different layers in the proposed three-dimensional model to avoid deadlock without prohibiting the use of any path. As such, Bi-Routing can improve the load balance and reduce the packet latency of an NoC. Compared with existing routing methods, experimental results demonstrated Bi-Routing’s superior performance with admissible area, power, and timing overheads.