Activated carbon fiber (ACF) was used to remove four kinds of trihalomethanes(THMs) from tap water which were remained as by-products during the chlorination of water. Adsorption capacity was investigated as a function of THMs concentration and solution temperature, and adsorption mechanism was studied in relating to the surface characteristics of ACF. All the four kinds of THMs were rapidly adsorbed on the surface of ACF by physical adsorption due to the enormous surface micropores and chemical adsorption due to the hydrogen bonds, showing a Langmuir type adsorption isotherm. Langmuir type is especially profitable for the adsorption of low level adsorptives. ACF was very effective for the removal of THMs from tap water because the THMs concentration is below $30{mu}g/L$ in tap water. The adsorption amount of THMs on ACF increased in order of the number of brom atom; chloroform, bromodichloromethane, dibromochloromethane, and bromoform. The adsorption capacity increased as increasing the number of brom atom due to the decrease of polarity in solution. The adsorption capacity of THMs on ACF can be enhanced by proper surface treatment of ACF.