The conception of dynamic effective paths is given. Combining the tree searching of depth-first,the orientation of searching the route,the strategy of spatial hierarchical reasoning and the node pricing function of A~* algorithm,an algorithm of searching dynamic effective paths is proposed by simulating the tree's growing.The delay time at nodes on traffic direction is taken into consideration in the new algorithm and is analysed to make dynamic traffic control and DVGS be fused more easily.The application of the new algorithm in DTA and DVGS is described.