Abstract: Large quantities of small textures significantly increase the costs of loading and rendering batches of 3D city models; slowing down the rendering efficiency.The traditional texture merging method relies on artificial experience which is inefficient.This paper introduces a multi-texture automatic merging approach based on the greedy and simulated annealing algorithms. Firstly，the greedy algorithm was used to merge the small textures automatically. Secondly，a simulated annealing algorithm was used to optimize the merged results in order to ensure that the results converged to the global optimum. The whole process of the texture merging is accomplished automatically. Finally，some experiments based on this approach are tested and discussed. Experimental results demonstrate the effectiveness of this approach.