The dissolution of microscopic voids trapped between fibers during the resin transfer molding process has been monitored previously by the image analysis technique. However, due to the difficulty of tracing simultaneously the interfaces among resin and several small air pockets in the convectional numerical techniques, the dissolution and distribution of the voids are still uneasily simulated. In this paper, we consider the resin flowing perpendicularly through the fiber bundle. A Monte Carlo-like random walk approach is developed to resolve the time-dependent, free-surface flows and to study the transport of tiny bubbles by tracing the paths of fictitious random walk, colored black or white. By decomposing the Darcy s law, which provides a strong correlation function between ∇P and K/μ, the local displacing probability of random walks can be determined. Being consistent with the experimental observations, the numerical results confirm that the voids can be classified into two types, namely, voids trapped in the fiber bundles and voids distributed among the fiber bundles. Through the proposed model, the simulated results show how certain parameters influence the collapsing rate of void, which is important for the void-free design considerations.