Composite foam sandwich structure has the advantages of light weight and high strength. Therefore, it is widely used in aviation. At present, the composite foam sandwich structure is usually formed by autoclave, but the manufacturing cost is high. In this paper, the technology of vacuum assisted resin infiltration (VARI), a typical low-cost representative of liquid forming, was studied. The experimental study was made on how to ensure the quality of products by adjusting the injection parameters under the condition of single side grooving with PMI foam, and the plane compression of VARI composite foam core with different grooving parameters. The results showed that the three mechanical properties of the test pieces with different slotting and punching parameters meet the application requirements.