The speeds of development and evolvement of sub-dialects and local dialects in Yi northern dialect are very different,which provides good compared materials for researching the development and evolvement trends of sound of Yi northern dialect. The compound consonant initials and compound vowel finals only exist in Suo Di sub-dialect,but are gradually disappearing. Only Yi Nuo sub-dialect to has open-up lip vowels,but they are in the process of disappearing. The pre-nasal voiced sounds have already weakened ...