In this paper, the Lattice Boltzmann Method (LBM) is used to simulate the seepage field of autoclaved aerated concrete blocks. The macroscopic permeability coefficients of aerated blocks are obtained. The complex flow characteristics of the internal flow field are revealed. A stochastic four-parameter growth method (QSGS) based on the distribution probability of initial growth nuclei and porosity is proposed. A meso-model of the real pore structure of aerated blocks is established. The influence of initial inlet pressure and model porosity on the permeability of aerated block is analyzed by numerical calculation of the permeability development process of aerated block. The results show that the two-dimensional meso-model close to the real pore structure of aerated block can be constructed by the stochastic four-parameter growth method; the water permeability coefficient of aerated block calculated by the LBM numerical method is in good agreement with the experimental results; under certain conditions, the linear relationship between the permeability coefficient of autoclaved aerated concrete block and its porosity satisfies the requirement of practical engineering application. It has certain guiding significance for practical engineering application.