This paper aims to describe the phonological and phonetic vowel features in Russian, Bulgarian and Korean. First of all, the author attempts the comparative analysis between bulgarian and russian vowel system from the view points of synchronism and diachronism. As it is described above, Bulgarian has 6 vowel phonemes(/i, e, a, o, ə, u/) while the Russian has 5 (/i, e, a, o, u/). As it is well known, Bulgarian and Russian have the same mother language(Common Slavic and Old Church Slavonic), but now they have different vowel system. This is caused from the different phonetic status of vowel in their language. So the author compares the acoustic feature(mainly, their formant 1, 2, 3), and gets the results as follows. As it is shown in the table, every figure of Bulgarian vowel formant(except /E/) is higher than Russian. It means that positions of Bulgarian vowel are located more back and more high in the oral cavity. This oral condition makes Bulgarian vowel be more independent than Russian and easy to pronounce the hard consonants. This also can be clue to explain the productive Russian soft consonants(because of their tounge positions - front and low and oral cavity). In the middle of main chapter, the author describes Korean vowel features and Formant value for the purpose of correct transcription and language learning. And also analysis it's rich phonetic system. The positions of Korean vowel are located more front and more high in the front vowel and the same position in the back vowel with Russian and Bulgarian vowels. In the end of main chapter, the author attempts to make the formal grammar model with the help of "Generalized Feature System and Unification Grammar" tools. For example: /ㅣ/ = {LAN 1}{CAT 1}{ROOT l}{FORM1 200}{FORM2 2100} /а/ = {LAN 2}{CAT 1}{ROOT A}{FORM1 755}{FORM2 1360} /ъ/ = {LAN 3}{CAT 1}{ROOT ə}{FORM1 450}{FORM2 1300}