“Zi Zhu” is a Chinese word for “self annotation” and is normally used by poets. This paper analyzed Su-Shi`s poems and its “Zi Zhu” in order to define the purpose and characteristics of “Zi Zhu”. “Zi Zhu” offers both objective and subjective informations. General helping informations in comprehending a poem can be looked upon as an objective whereas informations on poet`s daily life can be looked upon as a subjective. These informations are important in understanding the poems of Song Dynasty because the poems in that era reflects the daily lives of poets, so one can say that “Zi Zhu” is essential in comprehending the poems of Song Dynasty. The most important thing about “Zi Zhu” is that it is made for the third party. As being an annotation written by the poet himself, “Zi Zhu” has a stronger influence on the readers than other annotations. “Zi Zhu” helps the readers to comprehend and feel the nuance of the poet but at the same time it also restricts the liberty of interpretation, which leads to say that “Zi Zhu” has its duplexity.