This paper is concerned with the historical phonology of the Kan dialect. Three related problems are discussed: (1). the characteristic features of the Proto-Kan dialect; (2). the genetic relationship between Kan and Hakka dialects; (3). the historical development and variations of the Kan dialect. Among the views developed in this paper, it is emphasized that Kan and Hakka are originally two different dialects, a point which has significance for Chinese dialectology.