Abstract: The optimal preparation conditions for activated carbons from polyacrolynitrile ellipsoid powder by KOH activation were investigated by orthogonal experimental analysis. Results indicate that the activation temperature, holding time, KOH/carbon mass ratio all have a significant impact on the specific surface area, but a small impact on the total pore volume and mean pore size. The importance of factors determining (a) specific surface area are activation temperature > activation time > KOH/carbon mass ratio, (b) total pore volume are activation temperature > KOH/carbon mass ratio > activation time, and (c) the mean pore size are activation time > KOH/carbon mass ratio > activation temperature. The optimal combination of conditions (activation temperature of 800 ℃, holding time of 4 h and KOH/carbon mass ratio of 4:1) from orthogonal experimental analysis was validated experimentally. Under these conditions the specific surface area, total pore volume and mean pore size of the PAN-based porous carbon reached 2 517 m² g^-1, 1.07 cm³ g^-1 and 1.70 nm, respectively.