This research has two aims. The one is to describe tonal system in Pyeongchang dialect. Another aim is to elucidate the transitional features of changes in tonological systems based on Comparing Pyeongchang dialect and Jeongseon dialect. In conclusion, Pyeongchang dialect is a tone language and tonal system in Pyeongchang dialect is more unstable than that in Jeongseon dialect. There is some ground for this argument. First, these are interpreted to be the tone languages in Pyeongchang dialect. The base of judgment is as follows. a. The tonal systems consist of three toneme(plain tone, depart tone, rising tone) and have three tonemic patterns. b. The departing tonal pattern is only in a word with one syllable. c. There are peculiar tonemic patterns in tonal systems. we call yindeparting tone and yinrising tone. They occur in tone languages of Eastern Coast Korea. Second, the tonal system in Pyeongchang dialect is more unstable than that in Jeongseon dialect. There is some ground for this argument. a. There are two tonal rules both Pyeongchang dialect and Jeongseon dialect. One is the plain-2 pattern conversion rule of departing tone. Another is the freely change rule of the pyeongbok pattern. When tone is derive from the deep structure to the surface structure both rules has application. b.Sometimes the plain-1 pattern and the pyeongbok pattern is indistinguishable in Pyeongchang dialect. But they strictly distinguish in Jeongseon dialect. c. The pitch pattern is governed by intonation in Pyeongchang dialect. But it is not in Jeongseon dialect.