The microstructures of sesame cake under five applied pressures were measured using stereo light microscope and Image-pro software. Fractal dimensions of pore section border and pore size distribution were measured and calculated by the slit island process. Regression method was used to analyse the correlation between the fractal dimension and applied pressure. Results showed that the fractal characteristic of pore structure of sesame cake was obvious, the pore structure and its fractal dimension were significantly affected by applied pressure. There existed good linear correlations between applied pressure and fractal dimensions of the pore section border and pore size distribution. Their fractal dimension values decreased significantly with increasing applied pressure. It was concluded that with increasing applied pressure the pore section border is further twisty, the pore wall further rough, the pore shape further irregular and the pore size distribution further complicated.