The most ideal textile conservation is to block oxygen and light from historical textiles. However it is not possible because historical textiles should be examined, cleaned, restored, and exhibited to find out its historical value. Most of excavated costumes were severely stained and soiled. They are dark yellowish brown in color. To reduce the extent and intensity of the staining and to recover the original color of gray fabrics, bleaching would be required. Conservation treatment was carried out on the 8 historical costumes which belonged to General Duk-Ryung Kim(1567-1596). Two of them do not hold the fabrics. They hold only cotton wool and a little piece of fabrics. Even though these costumes underwent the conservation treatment in 1979, they were stained and needed re-treatment. This time, they were dual-bleached using hydrogen peroxide and sodiumborohydride followed by wet cleaning to reduce the soils and stains. The treatments improved the appearance of costumes. Through the analysis of the trace of fabric, carbonized fabric fragment, and fabrics remained in other garments, we concluded the missing fabrics to be ramie or cotton. It is different result from the primary report concluded to be silk.