A brain network in general comprises a substantial amount of short-range connections with an admixture of long-range connections. It is hypothesized that the length of connections is constrained by the spatial embedding of brain networks, yet fundamental principles that underlie the wiring length distribution remain to be elucidated. In this talk, by quantifying the structural diversity of a brain network using the measure of Shannon’ s entropy, we will show that the wiring length distribution across multiple species follows the maximum entropy principle under the constraints of limited wiring material and the spatial locations of brain areas or neurons. In addition, we will introduce a generative model incorporating the maximum entropy principle for network formation. This work provides a potential organizational principle of spatially embedded brain networks.