For　large-scale　unknown　environments,　a　method　of　topological　node　matching　based　on　visual　feature　is　presented,　and　a　local　scan　matching　strategy　is　integrated　to　realize　map　merging　for　multi-robot　system　under　RTM　(robot　technology　middleware)　framework.　A　main-auxiliary　structure　model　of　multiple　robots　is　developed,　and　an　improved　SP2ATM　algorithm　is　adopted　to　incrementally　constructing　topological　map　in　unknown　environments.　Based　on　this,　the　hierarchical　topology　structure　including　SIFT　(scale-invariant　feature　transform)　feature　information　is　presented,　which　is　combined　with　ICP　(iterative　closest　point)　algorithm　to　realize　map　merging　of　multi-robot　systems.　RTM　is　taken　as　communication　platform　to　improve　the　realtime　performance,　flexibility　and　robustness　of　the　system.　Simulation　on　USARSim　and　experimental　results　in　actual　environments　verify　the　effectiveness　of　the　proposed　method.