Hydrophilic activated carbon was prepared by a novel ethyl acetate hydrolysis method. Surface area analysis, spectroscopies, and microscopy were used to examine characteristic differences between raw and hydrophilic activated carbons. Results showed that hydrophilic groups were introduced onto the surface of activated carbon through ethyl acetate hydrolysis in an alkaline environment. The modified activated carbon exhibited higher water vapor adsorption capacity because the hydrophilic groups on its surface bound with water molecules through H-bonding. Adsorption isotherms of water vapor were well fitted by an adsorption model. The optimal temperature for thermal regeneration was determined to be 398 K.