Abstract: The route rationality and availability in path analysis is primary index to present navigator practicability, which is hardly researched at present. Based on subsection definition of route group and route availability index, the availability measurement model for path analysis is put forward using probability method. Supported by the model, a new modified Dijkstra algorithm named Mod-Dij is advanced after several path analysis algorithms are researched according to route availability. The route calculated by Mod-Dij is compared to Dijkstra’s result. It is shown that the route by Mod-Dij is availability clearly and can be used in real navigation widely.