The Sadu,a small ethnic group living in peripheral Yuxi city in southwest China,which has a population of 1505(2009).Government lumped them into the Bai nationality in 1958.However,their language is very unique,which is not intelligible to Bai,nor to the neighbouring Yi nationality. This study was conducted to investigate the current language use situation of the Sadu.Data discussed in this paper has been collected from door to door visits,questionnaires,interviews,observation as well as 400 core-word tests...