The invention discloses a method for establishing a network model based on a serial section image, belonging to the technical field of image processing and relating to a method for establishing a network model of characteristics of porous medium (rock) containing liquid such as underground crude oil, natural gas, underground water, and the like. The method is characterized in that a group of serial bidimensional section images inside a microcosmic model are processed so as to divide rock granules and pore spaces; on the basis of reconstructing three-dimensional images for the pore spaces, size distribution and topology information of pores and throats is extracted to finally establish a network model, therefore, image information is converted into the size distribution and topology information of the pores and throats in a three-dimensional space. The invention provides the method for establishing the network model based on section images of actual porous medium, has strong pertinence and high practicability, and can be effectively used for description and digital management of actual rock pore spaces and seepage characteristic thereof.