The current Jeju dialect holds the tone patterns of Middle Korean monosyllabic nouns phonetically. High tone, low tone, and rising tone of Middle Korean have been changed into low pattern, high pattern, and low pattern of Jeju accent. In this respect, the tone change goes along with Kyungsang dialect of Korea. But the change doesnot imply the phonological distinctive features, but the phonetic cues. The tone patterns have some influences on vowel duration and duration to the highest F0 peak. In other words, monosyllabic nouns with the rising MK tones represent the longest duration, while the low tones show the shortest duration. This means that the phonological tone patterns change into the phonetic accent. In this way, we can find some weak relationship between Jeju Korean and Middle Korean.