Abstract: Aiming at optimal congestion control,assigning proper routing layer resource and meeting other optimization objectives such as the number of layers and vias,a new layer assignment algorithm for multilayer routing problem was proposed.The algorithm consists of 3 phases：first,it acquires initial solution by heuristic approach,then optimizes the initial result by simulated annealing and at last,it optimizes resources of routing layer.The proposed algorithm was tested with industrial circuits and experimental result shows that the algorithm can accomplish proper layer assignment.