A most important function of railway yard interlocking system is to supply accessible and safe routes for train dispatching, namely route search. A railway yard can be modeled as a directed weighted graph according to the network of infrastructure and rule of train movement. Then the problem turns to a graph search problem. In this paper we presented two style of interlocking system both existed with different characteristics and supply areas. Then two graph search approaches, based on revised Dijkstra algorithm and heuristic search algorithm respectively, are adopted to satisfy the different demand for each system. This associated solution is presented to be well fitted for railway yard interlocking system. Experiment results based on real yard graph demonstrate its feasibility and effectiveness.