In order to analyze the micropore structures of active carbon, two types of surface fractal parallel plate models are calculated. It is shown that the disordered model, in which fractal surfaces are less restrictively piled up in the horizontal direction compared with the ordered one, can simulate the micropore size distribution of active carbon, The average micropore width L(av) can be expressed by L(av) = f(-Delta W/W) = g(n, D-s), where -Delta W/W is the percentage burnoff based on the ideally layered graphite model with the surface fractal dimension Ds = 2, and n is the number of the contraction mapping.