In the three-dimensional vehicular ad-hoc networks (3D-VANET)

high-speed moving vehicle nodes and changeable link states lead to unstable inter-vehicle communication links. Aiming at this problem

the time-space evolution graph model is constructed by introducing software define network technology to obtain network state in real-time and predict the process of time change and the link utility index is defined to quantify the wireless link performance. Then the weighted time-space evolution graph model based on link utility is established.Finally

the routing decision-making problem is transformed into a multi-attribute decision-making problem

and a link utility based reliable routing (LURR) algorithm is designed. Simulation results show that

compared with the existing four routing protocols

LURR algorithm has significantly improved packet transmission rate

end-to-end delay and routing load rate.