An ω-language is a set consisting of infinite-strings over some alphabet ∑, the ω-language accepted by some ω-finite state automation is called the ω-regular language.Several sufficient conditions for an ω-language is an ω-regular language are given by author from the point of view of the set in [4]. In this paper, author gives still from the point of view of the set a sufficient condition for an ω-language is an ω-regular language, i.e., if L is an ω-convex language, such that L=Adh(pref(L)) =Pref(L)Tail(L),then the L is an ω-regular language.Thus defined one subclass of the ω-regular languages class.