Abstract: Numerical simulation of resin transfer molding is important to mold design, process control and parameter optimization. This paper introduces the RTM process and its characterizations briefly. The governing equations of resin flow are presented. Based on the exposition of main problems of the commonly used methods in modeling the RTM process, the boundary-fitted coordinate system and the finite difference method as well as the resin flow domain decomposition process are employed to simulate the RTM resin flow process in the case of mold with interior insert. The successive resin flow front position,calculating mesh and the pressure distribution at the final stage are obtained, which is helpful for locating the air vent, and good agreement is found between the results and other investigations. The results indicate that the method provided by this paper is convenient and effective in solving the moving boundary problems with irregularly geometric boundaries.