Abstract: This paper collect all loan characters in Bamboo Slips Laozi of Han Dynasty, then look up the phonological position of these loan characters and their original character to examine and correct the phonological system of the Western Han Dynasty. The phonological system of the bamboo slips Laozi of the Western Han Dynasty is generally close to the The Book of Songs, a representative of the old Chinese phonology. At the same time there are some features initials of “xia” (匣)and “jian” (见) group belong to the same class; the relationship between the initials of “xie” (邪) and initials of “yu si”(喻四)is very close; the differentiation between unvoiced consonant and voiced consonant, aspirated and unaspirated is not so obvious compared with phonological system of Guangyun(广韵). As to rhyme, the evolution of the sound system in the Western Han Dynasty seems to have showed some signs, such as the evolution time of You (幽) Xiao (宵)and Hou(矦)can be traced back to the period of Emperor Wu of the Han Dynasty. The rhymes of bamboo slips Laozi of the Han Dynasty has most of the phonetic features of the Western Han Dynasty, at the same time, there are really some different features. We also found that rhymes analysis method has its unique value in the evolution of the text of Lao zi.

Key words: Bamboo Slips Laozi of Han Dynasty, the phonological system of western Han dynasty, loan characters, rhymes