Abstract: The modal particlesof Zhi只,xie些,si斯,si思,and zhi止 were the variants of the modal particle Xi 兮in that all of these particles expressed the same modal,applied in the same grammatical unit,and were documented complementarily in spite of their phonetic difference.At the same time,Xi 兮 was a variant of modal particle He 呵.The pronunciations of these modal particles were different from each other which actually reflected a certain degree of sound changes in old times.The actual phonetic changes in ancient spoken Chinese were far more complicated than detected from the existed written classic literature.Regarding the fact that modal particle does not carry the meaning of a “real” word,its character form in ancient time easily changed as its pronunciation changed in ancient poems

Key words: Modal particle, Historical sound change, Xi兮, Zhi只, xie些, si斯, si思, zhi止