Effects of maleinated compatibilizer and heat treatment on the internal structure and physical properties of PP/organoclay nanocomposites were investigated by using various measurements, e.g., SAXS, TEM, DSC and DMTA, and rotational rheometer. Experimental results showed that maleination and heat treatment affected the internal structure and dynamic mechanical properties of PP/organoclay nanocomposites. Storage modulus and loss tangent of PP/organoclay nanocomposites were strongly related to the compatibilizer loadings and heat treatment conditions because the interfacial structure between PP molecular chains and organoclay particles had been changed by the addition of compatibilizer to PP/organoclay nanocomposites. DSC and DMTA results of the compatibilized nanocomposites and effects of heat treatment on crystallization and dynamic mechanical thermal properties demonstrated that there is a small change in the glass transition temperature because the chain mobility and free volume in the amorphous region are increased by heat treatment. It was found that heat treatment imposed influence on both amorphous and crystalline regions of PP/organoclay nanocomposites.