The question on how vowels are structured or organized with relation to their systems in natural languages is one of primary concerns to phonologists. This paper analyses the vowel patterns according to the number of 3 to 7 vowels of languages based on UPSID451 with the phonetic and phonological view. Through the discussion of main topics we firstly reconfirm the fact that the 3 vowels at the corners of the conventional triangle, /a i u/ are the most widespread. We also see that vowels are added regularly in an ordered way as the systems expand, and thus two mid vowels either /e o/ or /ε ɔ/ are added in 5 vowel-systems and so on. In addition to these well known facts, we see that the front vowel is preferred to the back vowel in majority of the 4 vowel-system. We also find that additional segments are positioned to the direction in which the vowel systems prefer to maintain the numeral symmetry of front and back in their height with the priority of peripheral area of the vowel space, and then the interior area. It is from this fact that in the majority of 4 vowel-systems the front mid unrounded vowels are preferred, and the central vowels are taken in many 6 vowel-systems as an additional segment. (Hankuk University of Foreign Studies)