“内外转”是汉语早期韵图的重要分析范畴,对其含义的解释历来纷纭不一。本文以罗常培先生(1933)的主要元音高低说为依据,论证了内外转的韵图分布及其音理依据,提出了内外转为相关韵摄间主要元音对比的看法。文章还就早期韵图所表现的语音系统的性质进行了讨论,提出了早期韵图音系只表现《切韵》系韵书音系的看法。 “Internal and external transfer ” is an important category of Chinese early rhyme analysis, the interpretation of its meaning has always been different. This paper, based on Luo Changpei’s main vowel level theory, proves the distribution of rhyme diagrams and their phonetic basis, and puts forward the opinion that the internal and external vowels should be compared with the main vowels. The article also discussed the nature of the phonetic system represented by the early rhyme diagrams and put forward the view that the early rhyme phonological system only displays “Rhyme” rhyme system.