FOREST is a new double-layer channel router based on Unconstrained Via Minimization. It partitions the routing procedure into two parts: Topological routing and Physical routing. As a heuristic algorithm, it tries to consider the routing completion rate, area, vias and wire length as a whole. It allows horizontal segments and vertical segments to route on one layer and allows over lapping of segments on different layers. FOREST is useful for general channels, especially for irregular channels. Some examples show that it is efficent,especially in reducing vias.