With relevance theory and coherence theory as the theoretical basis, this paper studies the pragmatic function of Chinese-Utterance final particles: a, ba and ne and claims that the discourse function of ne is stronger than a and ba. In other words, the modality meaning of a and ba is stronger than ne. This paper also studies the reason why a, ba and ne have different pragmatic functions and concludes that the meaning of ne is mainly the meaning of mood, ne has a longer history and the grammaticalization of ne is more complete while a and ba have obvious modality meaning; they have a shorter history than ne as mood particles and their grammaticalization still continues.