Abstract: According to the characteristics of VARTM, the mathematical models of resin flow and preform deformation during the mold filling process were built. A mold filling simulation algorithm based on mixed grid approach was proposed. In this approach, the geometry model of the mould cavity was meshed by 2D or 3D grid, and then a 1D affiliate element was added on each surface element of the vacuum bag to absorb or extrude some resin in real time cased by the vacuum bag deformation, so the mixed grid simulation model was established, During the simulation, resin flow and preform deformation were solved separately, then they were coupled using the above-mentioned mixed grid simulation model, the unity of simulation precision and velocity was achieved. A mold filling experimental platform for VARTM was built and a 1D mold filling experiment was implemented, according to the comparison between simulation and experiment results, the validity of the algorithm was verified. At last, the feasibility of the above-mentioned algorithm on 3D complex structure and sequential injection strategy was validated by 3D simulation example.