Phonetic Complement of the homophone system in ShuoWencame from different periods. The Character-building ability of the same phonetic complement is different in different periods. According our study, more than half of the phonetic complements in ShuoWenhave already existed in the Shang Dynasty. Only 10%-20% of the phonetic complements were appeared in the other periods. Almost a third part of characters which existed in the Shang Dynasty were largely chosen as phonetic complement at that time.