Even though the Chi-tan Dynasty was a country that destroyed the post-Qin Dynasty and controled the ruling position, it was not noticed in spite of a position of the so called-barbarian (Ho) in China, However, when seeing the costume legacy of the Chi-tan in the tenth-twelfth century, we could understand that they had their own characteristic, the sophisticated weaving skill and a bright costume. This study considered the costume of the Chi-tan Dynasty in the tenth-twelfth century based on the literature after seeing the Hangzhou Silk Museum in 2004 and the Chi-tan special exhibition in the Kyushu on October of 2011. This article examined the double costume structure of the costume system of the country and of the Han time for that era, and each costume characteristic for a robe, a top, pants and boots in the general costume. In addition, it tried to find the relationship between the netted clothes and a mask which it was used in their own aerial sepulture in the Chi-tan Dynasty and the costume of Goryeo Dynasty. The result of this study would be a useful data for having a new view of the costume of the Chi-tan (Laio) and understanding the relationship with the costume of Goryeo Dynasty. The result is as follows:1. The costume of Chi-tan (Laio) Dynasty in the tenth-twelfth century was taken a double structure referred to the Emperor-the south bureaucrat -the costume system of the country and the Emperor-the north bureaucrat-the costume system of the country by accepting both the costume of Chi-tan as the costume system of the country such as a fitted robe, a long robe and Left-overlap fasten, and the system costume of Han time. 2. The costume was consisted of a fitted robe, a long and a short robe of Left-overlap fasten as an upper garment, and added the leather-fur robe. For pants, persons of both sexes wore shorts pants, most men wore the traditional socks and long pants that had a shoulder strap, and women wore a skirt that had a shoulder strap. 3. Boots of Chi-tan had the round top of a shoe, so it was suitable for using a stirrup. It was made into a curve of the front center of ankle of a shoe so that it could minimize the air resistance and could not get damaged by friction. 4. The funeral custom in Chi-tan was cremation after having the top of tree funeral. Therefore, the body was put a net long robe for protecting to lose the body for 3years in the top of tree funeral. The face was got a mask, the material of a mask and a net was classified depending on social status. 5. As there are many probabilities between the costume in Goryeo Dynasty and one of Chi-tan, this study would be helpful for researching the costume in Goryeo Dynasty. The hair of Chi-tan man was ‘Gonbal’ that the front hair was a shaved head and the back hair was tied, they didn’t wear a headgear but a nobleman in their daily lives, unless it was for keeping out the cold and the wind. We think that the most efficient of the costume pattern and the way to wear in Chi-tan was realized in the real life for riding a horse; we could consider the hair style that shaved the front hair and the custom in which they didn’t wear a headgear in the daily life in the same vein as well.