Modern society is age of sports just as health and leisure became dominant concern, which has caused the fixation and development to sports wear considered as fashion for everyday dress. This paper focused on the development process and aesthetic characteristics of knit design expressed in the 20th century sports wear. The importance and direction of knit design in modern sports wear is expected. Style, items, fabrics, colors, details and top designers were analyzed in sports wear from the 1910' s to 1990' s. Sports wear can be categorized into two of the active sports wear and spectator sports wear. Since disappearance of division between ordinary wear and sports fashion in the 1970' s, the functional wear of leggings, cycle shorts, exercise clothes, leotard, and leg warmer appeared. Vicennial developments of synthetic fibers and new fabrics have caused the great changes in knit design. Colors were vivid in the 1950' s, metallic in the 1970' s and neon in the 1990' s. Sportive sense was expressed by various details. The dominant knit designers who expressed aesthetic characteristics to sports wear were Coco Chanel, Claire McCardell, Balenciaga, Andre Courrege, Pierre Cardin, Yves Saint-Laurent, Ralph Lauren, Donna Karan, and Giogio Armani.