In the design of digital system, designers use multi-layer LSI to connect all signal sets between circuit modules. This paper suggests how to minimize upper street congestions and lower congestions in the single-row routing, a routing method of multi-layer LSI. This paper suggests the heuristic algorithm which minimize upper street congestions and lower street congestions by suggesting interval graph and relational operator and finding out of the order of signal sets The algorithm was implemented on a VAX-11/780 computer and illustrated by means of examples.