For corpus-based speech synthesis, large quantities of labeled speech are required. Manually labeling speech data is quite labor-intensive. Therefore, automatic speech labeling is highly desired. Prosodic break detection is one of the tasks for automatic speech labeling. In the paper, we propose an automatic break detection algorithm for mandarin Chinese speech. In this approach, we use energy contour to normalize duration of syllables and use the concept of normalized transition time to represent the time interval between two syllables. A recursive algorithm is then used to select locally longer intervals as pauses. Language specific constraint rules are also used to produce a better judgment. The automatic break labeling results have been proved to be good.