Abstract: Mold-filling simulation of unsaturated flows in liquid composite molding(LCM) is important for optimizing process parameters quickly and cost-effectively in the virtual space. A dual-scale computational model for simulating unsaturated flow of dual-scale fiber mat under isothermal conditions was presented. The macro-micro flow control equations were solved by introducing the sink function, and the influence of capillary pressure in microscopic immersion was considered. The numerical simulation of unsaturated flow was realized in the finite element/control volume algorithm. The 2-dimensional radial filling experiment was carried out on the triaxial stitched fiber mat. The experimental results were compared with the numerical simulation predictions and the results show that the method can accurately simulate the unsaturated flow in the dual-scale fiber mat. Based on this calculation model, the effects of fluid viscosity, injection flow rate and the tow porosity on the unsaturated filling process were discussed. The results show that different fluid viscosity, injection flow rate and tow porosity have different effects on the length of unsaturated region, the inlet-pressure history and the filling time during filling process. The research results can provide guidance for reasonably prediction of filling process and the inlet-pressure history.