Through the alkaline treatment of MMT, caprolactam sodium, being the catalyst of monomer casting nylon, was generated between MMT layers. The MMT/MCPA6 composites were prepared. The structure and properties were characterized by TG, DSC, HDT, SEM and mechanical properties. The results showed that the alkaline MMT could induce the generation of nylon γ crystal and increase the crystallinity of the material. The γ crystal content increased with the increase of MMT content. MMT performed a thermal barrier effect, so that the thermal decomposition temperature of the composite material was improved, with the increase in carbon yield. The thermal decomposition temperature of the composites was enhanced to 231℃ and the heat distortion temperature increased to 114 ℃. Alkalized MMT kept the toughness of the composite at a certain level, resulting in a significant increase in strength.