Using the concept of 'functional load' introduced from traditional linguistics, we described research value, calculation conditions, measuring unit and calculation method of functional load in detail from the point of view of phonetics, phonology and linguistic, by combining the three common distribution of phoneme system, using Huo Kaite and Greenberg measurement methods, Shannon communication theory and the concept of linguistics. In this paper, we use Tibetan Lhasa Dialect phonological system as research object, analyzed and studied the structure and distribution of phonological, and it shows that each phoneme of Tibetan in a system have their own position which can better quantitative description and reflect essence and variety of the synchronic and diachronic of language.