Abstract: In this paper we present that CAS--SYL, a subeorpora of the CAS Chinese Speech Database,which includes total l,267 Chinese isolated syllables read by 10 speakers, has been labeled by a well trained transcriber. Labeling level is at semi--Syllable level, it's mainly due to the initial/final construction of Chinese syllable. The phonetic symbol system adopted to annotate the utterance segment is SAMPA--X for Chinese. Placement of segment boundary and labeling strategies are presented. We also show the clues of GCI implicating in speech waveform that can used to refine the boundary of segment. The acoustical realization of crvarticulation happening in the transition from initial to final is summed also.And the factors resulting of the inconsistency of manual segmentation are discussed.