This dissertation is a comprehensive monograph on Li Keran's (1907-1989) art and career. The author had been a student of Li Keran for more than sixteen years and this work contains many original materials which have not been previously published. Li Keran is one of the most influential figures in history of twentieth-century Chinese art. He is called the reformer of Chinese landscape painting, and his art has been recognized as a milestone in the development of Chinese painting in this century. Reformism and traditionalism are the two major streams in modern Chinese art history, and there was no other artist like Li Keran who had been a leading figure in both of the two major artistic streams at his time. His unique position between the two major streams determined his thought, art theory, and painting style. The dissertation is divided into an introduction, seven chapters, and a conclusion. Chapter 1 is a general discussion of the historical and cultural background of Chinese art from the later nineteenth century to present century. Chapter 2 is a more in-depth biography of Li Keran, in which some gaps in Li's early life have been filled and some inaccurate information found in extant publications has been corrected. Chapter 3 examines the evolution of Li's philosophy of art, his synthesis of Chinese thought and Western ideas, and the major contributions he made to Chinese art theory. Chapter 4 discusses the transformation of Li's painting style, divided into seven stages. Chapter 5 analyses the formation of Li Keran's painting techniques, and Li's innovations upon them. This chapter also discusses the connoisseurship problems related to Li's work, and provides some guidelines for identifying authenticity. Chapter 6 gives an account of Li Keran's influence on other artists, leading to the formation of the Li School. Chapter 7 reviews the critical appraisal of Li Keran's art, and lays special stress on the phenomenon of changing attitude towards the artist. The conclusion provides a summation of Li Keran's art and career as a whole.