Under the background of Big Data， the link impedance of road network is repre-sented by timeslice successively in the form of Time-Aggregated Graphs， which simplifies the spatio-temporal network， and the dynamic shortest path model based on the departure time with time window is constructed.At the sametime， the concepts of feasible links and feasible paths are put forward， and the improved reverse labeling algorithm is designed.The improved algorithm can simplify the search process， and quickly find the optimal departure time and the corresponding shortest path which meets the requirement of the time window.The model and algorithm is tested with a simple network and the result shows the proposed model and algorithm is effective and reasonable.