The modal particle＂o（哦）＂in Sichuan dialect has its own unique expression of modality meaning, and it has a completely different identity to the Chinese national language. This paper discusses the modality function and the politeness value about Sichuan dialect modal particle＂o（哦）quot;in order to regulate the use of＂o（哦）quot;in the dialect and provide some theory basis for other similar modal particles used in the Chinese national language.