Experiments showed that the variations of the amount of steam, temperature and time has great effects on the decoloring power for methylene blue and yield of activated carbon obtained from commercial hardwood charcoal by steam.Activated carbon with improved decoloring power 170ml/g of 0.15% methylene blue solution obtained from commereial hardwood charcoal are manufactured in the following optimum conditions: amount of steam l:1.31-charcoal(g): H2O (ml); activation temperature 900℃; activation time 4 hrs. Then the yield of activated carbon is 15%, and 44% of activated carbon with methylene blue absorptivity 110ml/g could be obtained from commercial hardwood charcoal by activation with steam(1:0.87) at the temperature of 850℃ for 2hsr.