After swelling, preformed particle gel (PPG) can be suspended in the aqueous phase to plug small pores while flowing through the formation or deform under large pressure gradients to move further into the formation, and achieve in-depth profile control. This paper, based on the size exclusion theory, introduces the concept of the critical pressure gradient to capture the phenomenon that PPG plugging small pores can deform and pass, and the concept of the mean number of bridging particles and mean bridging probability to characterize the bridging of the PPG inside large pores. On this basis the numerical simulation model of the PPG flowing through porous media, combined with the numerical simulation theory, has been established and validated with physical simulation experiments. The general regularity of the PPG migrating inside porous media is then studied using the proposed numerical simulation model.