This thesis tries to clarify the value of sketching in art, and to find what the sketches mean to Lee in his artistic career. It studies the materials and forms in Lee Taz-Fan's sketches from the point of Rollo May's idea -- artists produce their works from the encounters of their life. According to the analyses, a sketch is not only visional depiction but also a kind expression of symbol or emotion. Lee chose the contents of a work from encounters with his life. He used various forms of line in sketch to express the scenes in his mind or the fluttering in his living world. In the contrast between his sketches and pantings, each work shows a unique quality. Especially, Lee's sketches show his encounters in details. They also inspire the audiences to face their life and the nature from an new insight. Appreciating Lee's sketches is just like talking with Lee himself.