A language is a system of pure values, and its pure nature refers to the one which language is in opposition to the sciences concerned with values, and bears no natural connexions with the things outside the system. Linguistics is in opposition to economics and the study of writing system, for the connexions of the latter two with the things outside the systems are inevitable. The language system of pure values has fortuitous and collectively conventionalized characters. The pure nature of language system is of great importance, for it can enable us to avoid some erroneous tendency in the study of language, to further clear the object of language study, and to better understand the nature of language.