This article examines line as the fundamental expressive element of Chinese mountain and water painting and argues that it embodies the national character and cultural spirit of China. The author first shows how painters abstract different line forms from nature to create images that convey their inner meaning, and discusses the four aspects of the “bone method” (gufa yongbi): framework (gujia), momentum (gushi), substance (guzhi) and control (guli). A historical survey traces the development of line from the outline-and-colour manner of the Tang dynasty, through the appearance of texture strokes (cunfa) in the Five Dynasties and their combination with line in the Song, to their culmination in the Qing. The national character of line is then explained by three factors: the particular materials of Chinese painting, notably the soft brush, ink and xuan paper; aesthetic tastes shaped by Confucianism, Daoism and Buddhism; and the shared aesthetics of calligraphy and painting, emphasized since the rise of literati painting. Finally, the author maintains that line remains the basis for expressing national identity, and that contemporary painters should innovate in step with the times while preserving the essential role and national characteristics of line.