Using the method of melt intercalation, nanocomposites of polyamide 6 with three molecular weight and national organoclay were obtained and the effect of the molecular weight of polyamide in the mechanical and rheological properties was studied. It was used a modified clay with quaternary ammonium salt (Cetremide) and characterizations were made through the techniques of infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results showed the incorporation of the salt in the clay and in its organophilization. To obtain the nanocomposites, a master of PA6/clay (1:1) was prepared and was added in the polyamide 6 in amounts of 3 and 5 wt% clay using a co-rotational twin screw extruder. The nanocomposites were injection molded and evaluated by capillary rheometry, XRD, transmission electron microscopy (TEM) and mechanical tests (tensile and impact). The results of capillary rheometry showed that the presence of 3 and 5% of organoclay in the PA6 increased viscosity of the systems. It was observed that higher molecular weight matrices and also to higher clay content showed higher shear stress and therefore higher viscosities as compared to other systems. It was also seen that the viscosities of the nanocomposites are smaller than those of pure polyamides, which implies a better processability of the material. The results of XRD and TEM showed that the systems were predominant in exfoliated structure. As regards the mechanical properties under tension it was observed that the molecular weight influenced on the properties of polyamide 6, that is, the higher the molecular weight, the greater the result of properties, while that the impact strength decreased.