For geographic routing in 2D ad hoc networks, greedy algorithm is efficient. The next hop node is selected according to the distance to the destination. However, greedy forwarding fails when a message reaches a local-minimum. Face routing is used to solve these problems. Unfortunately, these results cannot be applied to 3D networks directly. We propose an algorithm GSG (Greedy Surface routing Greedy) for geographic routing in 3D environments. We partition whole network with 3D Restricted Delaunay Triangulation. Triangles and isolated edges are defined as 3D components on Surface. By means of identifying intersecting triangles and edges, efficient routes are constructed on surfaces by bypassing local-minimums. Simulation results show that GSG achieves good routing performance and scalability.