We see from the vowel systems of the world that vocalic phonology generally consists of the three basic vowels, /a i u/ and some other vowels in an ordered fashion. Nevertheless, it is obvious that vowel system of one language differs from another in number of vowels it contains and its inventory. It is well known that vowels are basically classified by the three conventional parameters for vowel description, namely height, position in a front-to-back dimension and lip-rounding. One might say based on this that different vowel systems are different in the three primary parameters. However, a simple description on whether or not a specific vowel, say the high front rounded vowel /y/ is present or absent in a system cannot judge whether the system is universal or very isolated. The question that then arises is which types of vowel system are more universal, and what determines whether the system is universal or not. This paper aims to develop and provide an evaluation model or standards for the vowel systems of natural languages. The model in this paper consists of six standards, two from the property of vocalic typology in relation with number of vowels, and four from the three conventional properties for timbre of a vowel sound. The two standards, [Number of vowels] and [Vowel inventory] fall into the former, and the standards, [Lowness], [Equilibrium and Symmetry], [Frontness] and [Lip roundness] into the latter. (Hankuk University of Foreign Studies)