A series of polyacrylamide (PAM) organoclay nanocomposites were synthesized by in-situ intercalative polymerization using acrylic amide, sodium hydrogen sulfite, and ammonium peroxydisulfate in the presence of various contents of metakaolinite (MK) modified with potassium acetate (KAc). Both x-ray diffraction data and atomic force microscopy images of PAM/MK nanocomposites indicate that the MK was homogeneously dispersed on the nanoscale into the polymer matrix. Infrared and Raman spectroscopy indicated the formation of hydrogen-bonding interactions between PAM and MK and the distortion of the Si-O tetrahedron and Al-O polyhedron in the polymerization process. In addition, DSC results revealed that when the nanocomposites with MK modified with KAc were less than 10%, they have higher decomposition temperature and better thermal stability in comparison with the pure PAM.