Activated carbon could be prepared from residue of rice husk using physical activation with steam as activating agent. Response surface methodology (RSM) was applied to optimize the effects of processing parameters, and regression analysis was performed on the data obtained. The optimal conditions for adsorption capacity of activated carbon from the residue of rice husk were activation temperature of 946 ℃, activation time of 31 min and water (18 g) which changed to steam by heating, resulting in 970.06 mg·g^(-1) of iodine adsorption capacity and 31.36% of activated carbon yield. The activated carbon prepared under optimum condition was mesoporous with BET surface area of 1,004.296 m2·g^(-1), total pore volume of 0.9388 cm3·g^(-1) and average pore diameter of 2.043 nm. The surface chemical functional groups of activated carbon were identified by FT-IR, and its microstructure was examined by scanning electron microscopy (SEM). We concluded that the process of physical activation with steam could be an environmentally harmonious and effective method for preparing activated carbon from residue of desilicated rice husk.