To explore the mechanism of pull-out group anchor effect of anti-floating anchor rods and improve the anti-lifting bearing capacity of anti-floating anchor rods. A micromechanical model for the pull-out bearing capacity of anti-floating anchor rods was established using contact mechanics methods, and a discrete element model was established using particle flow theory to analyze the mechanical properties between anti-floating anchor rods and rock and soil under different working conditions. The results show that when the distance between anchor piles is 4D, 6D, and 8D, both axial stress and shear stress show an initial increase followed by a decrease, and finally tend to stabilize. As the pile spacing increases, the axial stress between the anti-floating anchor rods shows a trend of first increasing and then decreasing. As variation time step increases, the porosity at different positions shows a trend of first increasing and then stabilizing. The analysis method based on particle size model can effectively analyze the group anchoring effect of anti-floating anchor rods, providing technical means for underground structural engineering construction and safety management.