The preparation of activated carbon (AC) from bamboo stalks activated by 25% KOH solution was used to investigage the adsorption of methyl orange solution (MO). The MO adsorption capacity of AC  depended on the AC  preparation conditions such as temperature and calciantion time. As theresults, the sample of AC heated at 800oC for 120 minutes had the best ability to adsorb MO, and not much weight loss. The MO adsorption of AC were conducted with the following parameters such as AC weight of 0.03g; volume of solution MO of 50 mL; pH ~ 2.0; shaking speed of 200 rpm; adsorption equilibrium time of 60 minutes at room temperature (25 ± 10 °C). The maximum adsorption capacity calculated by the Langmuir isothermal model was 312.5 mg/g at 25oC.