The Kháng people are a community residing in the Northwest region of Vietnam, primarily along both sides of the Đà River. Due to their small population and relatively scattered settlement, often interspersed with other ethnic nationalities, the Kháng language is used only within families and villages, mostly by older generations. Without formal instruction or the development of a written literary tradition, the Kháng mother tongue is at high risk of extinction. This book presents the results of a study on the phonetics of the Kháng language and proposes a writing system for the Kháng people in Vietnam.