Nowadays, FRP have played an important role in modern industry. The core material is always used in FRP to improve the bending stiffness. For large FRP structures, the manufacturing method will be VARTM. This study is to investigate the property of resin infusion in sandwich structures. After understanding the process of infusion, the permeability parameters could be established and to check the accuracy by using the simulation software, RTM-Worx. Through the method of simulation, we could get the combination permeability of core and fiber. Using the software to predict the actual situation and find out the appropriate injection strategies will make the refusing process more efficient. Finally, if we intensively realize the character of sandwich structures in VARTM process, it will be a great benefit for constructors. However, that will improve the competitive ability, too.