Abstract: Labels are an important ingredient in map. Whether labels are in place or not it plays an important role on the readability and usefulness of a map. However, in computer cartography, it is common knowledge that the labeling effect and speed are not ideal yet. Today, even though some other areas of computer cartography have been greatly improved, the automatic label placement is still a great problem. So more researches should be put into label placement. But recent mathematical analysis of cartographic label placement task has shown that finding optimal labeling is prohibitive due to the inherent computational complexity of the problem. This result implies that seeking an efficient algorithm for optimal label placement is a hopeless task. What we can do is to find near-optimal labelings in a reasonable time. This paper provides an optimal labeling algorithm based on backtracking,the algorithm has been put into practice and gotten better effect than some other optimal labeling algorithms.