This paper proposes an efficient image collage approach called TrCollage using tree-based layer reordering, which takes into account not only the efficiency of the collage processing but also the quality of the final collage effects. Besides, our tree-based TrCollage also meets the enhanced demands from the rapid development of mobile technology, which call for robust solutions for efficient picture collage without computation-intensive processing, e.g. graph-cut, saliency detection. The experimental results have shown the efficiency and effectiveness of our tree-based TrCollage with high-quality image collage effects applying layer reordering.