Efficient　automatic　guided　vehicle　(AGV)　scheduling　is　the　key　to　increase　the　throughput　of　automated　container　terminals.　Traditional　transport　strategies　cannot　guarantee　that　AGVs　are　fully　loaded　during　their　traveling　between　the　dock　and　the　container　yard,　which　leads　to　the　insufficient　utilization　of　AGVs.　A　load-in-load-out　AGV　route　planning　mode　provides　two-way　loading　between　the　dock　and　the　container　yard　and　thus　improves　the　efficiency　of　container　terminals.　In　this　paper,　a　load-in-load-out　AGV　route　planning　model　is　designed　with　the　help　of　a　buffer　zone　where　an　AGV　can　carry　at　most　two　containers.　A　simulated　annealing　algorithm　is　used　to　solve　it.　Comparisons　with　the　popular　generic　algorithm　and　particle　swarm　algorithm　are　made.　Simulation　results　show　that　the　proposed　algorithm　can　effectively　solve　the　problem　and　realize　the　bi-directional　loading　of　AGVs,　which　is　of　great　significance　to　improve　the　efficiency　of　the　production　of　automated　container　terminals.