The dyeing characteristics of acorn was investigated. The natural Fabrics-cotton, rayon and silk-were dyed repeatedly in the solution extracted from acorn, CuSO_4,, K_2Cr_2O_7, and brine were used as mordants to improve color fastness. Anti-bacterial property was measured in the dyed and mordant treated fabrics. When the cotton and rayon fabrics were dyed and treated with CUSO_4,, their colors showed very clear. They also had good color fastness and excellent anti-bacterial property. The dyed silk fabrics had better dye absorption property than the cotton and rayon fabrics without mordant treatment. But the fabrics dyed without mordant treatment had low light fastness. The cotton, rayon and silk fabrics dyed and treated with brine were dark and unclear. An aftertreatment with CuSO_4 and K_2Cr_2O_7 made the dyed fabrics darker and more clear.