The Derung People, as an ethnic group with the smallest population among the ethnic minorities in Yunnan Province, live in a highly compacted community along the Derung River in remote northwestern Yunnan. Through a questionnaire survey and interviews, the current study examines the mother tongue competence of Derung villagers in the Dulongjiang Township. The findings show that the majority of them are able to communicate with members of their community in Derung, but, in comparison to their fairly higher oral and aural proficiency, only a limited number of Derung people acquire native literacy. This lack indicates that the popularization of the Derung script is far from satisfactory in Dulongjiang Township. In order to identify factors underlining this discrepancy, SPSS19.0 is employed to perform a quantitatively analysis of the data. The analysis demonstrates that their oral and aural competence goes up with age and goes down with their educational level, while their literacy competence is most positively associated with the cohort of 20-39 years old, males, and downstream residents.