Polyurethane/modified kaolin foam composites were prepared via in situ polymerization with calcined kaolin as well as intercalated kaolin by one-step procedure. The lattice structures of the kaolin were characterized by XRD. The calcined kaolin under 600°C became amorphous structure and were well dispersed in the polyurethane (PU) matrix. The interlayer spacing of intercalated kaolin with potassium acetate shifted from 0.715nm to 1.407nm and were occurred clusters in the PU matrix. FTIR showed that the two kaolin had tiny effect on the structure of the PU and the hydrogen bonding played less role on mechanical performance. The mechanical properties induced by the addition of both of modified kaolin were analyzed. The mechanical properties of the foams with calcined kaolin were better than that with intercalated kaolin. The distribution of modified kaolin were analyzed by TEM. The dispersed particles of calcined kaolin were smaller than that of intercalated kaolin and the dispersion of kaolin played more role on mechanical performance.