The purpose of this research to look into formative characteristics of eco T-shirt design. Previous study researchers have mostly focused on overall eco fashion design, but on the other hand the research on eco product entity leaves much to be desired. We analyzed formative characteristics of eco T-shirt design that is easily accessible in real life and is easy to passing message. We selected 23 eco brands through internet and analyzed total 500 photos of eco T-shirt. Each photo was categorized by sex and the nations which belong to the eco fashion world associations. The content and statistical analysis was used for data analysis. The content of the research is as the following. First, it was found out that basic straight silhouette, achromatic color, human pattern, plant pattern, and eco-friendly organic material were used for the design of eco T-shirt. Second, it showed difference of silhouette, color, pattern according to nations. Third, it showed difference of silhouette, color, pattern according to sex. Fourth, symbolism of eco T-shirt was nature love, nature support, society ethicality, anti-sociality, and economics. This research aims for providing practical help and assistance to the development of eco T-shirt and its relevant industries.