Abstract: The existing discretization methods for moving-constrained trajectory have some defects such as inefficiency,non-intuitiveness,and susceptibility to loss of movement patterns. A novel discretization method that is based on road network construction and road matching is proposed. First,the road network from trajectories based on mathematical morphology theory is extracted. Next,it matches the trajectories to the grids on roads and changes the trajectories into grid sequences. Finally,the trajectory patterns using the maximal frequency sequence pattern mining method are detected. Experimental results show that this algorithm can quickly and efficiently discretize trajectories and detect more detailed trajectory patterns than the other algorithms.