The macroscopic properties of a material are closely related to its microscopic porous structure. Many techniques have been developed to characterize the microstructure of porous solids. Among them,. the simple gas adsorption techniques give the greatest amount of information. It was recently  recognized that the fractal geometry and percolation phenomena might be used to reveal the complex structure of porous materials from adsorption  experiments . In this article, the  determination of surface fractal dimension and the evaluation of the pore connection of porous solids through the fractal and percolation analysis of nitrogen isotherms, respectively, are reviewed. The emphases will  placed on the applications and limitations of fractal and percolation analysis to the real materials.