The purpose of this study are to observe the variation of vowel space on Daegu dialect through the Acoustics Phonetics by using speech style. Data have been collected from 53 informants by interviewing the subjects. In this interview, I used two different formats of speech style. One format was spontaneous speech and the other was reading speech style. After analyzing results of the interview, I measured the vowel formants by using the Praat program. Using the results, I analyzed the statistical analysis by informants` age, speech style and the vowel position of prosody units. As a results, there are differences in the informants by speech style. There were reducing vowel spaces in the reading speech style to the spontaneous speech style. When the vowel space is reduced the /a(ㅏ)/ raised, the /i(ㅣ)/ backed and /u(ㅜ)/ fronted. When the age category in the reading speech style is low the vowel space tends to expand. When the age category in the spontaneous speech style is not valid in the vowel space variation.