This study investigated the potential application of heavy oil burning fly ash as a precursor to prepare activated carbon. The raw fly ash obtained from a power plant is cleaned by nitric acid / hydrochloric acid and activated at 550- 800 °C with hold times of 30 and 60 minutes to obtain fly ash activated carbon. The phosphoric acid is used as a chemical agent to improve the surface characteristics of the cleaned fly ash. The effects of process variables such as amount of chemical reagents, activation time and temperature were investigated according to two levels full factorial design. The resultant activated carbons were characterized in terms of Brunauer, Emmett and Teller (BET) surface area and total and pore volume. The maximum specific surface area was found of 148.30 m2/g at 800C temperatures with 60 min holding time. The test showed that the surface area and pore volumes of the material are also significantly enhanced by the activation process.