Attapulgite fibers were modified by polyurethane, forming polyurethane grafted attapulgite (AT-PU), which was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Nylon 6/AT-PU nanocomposites of different modified attapulgite loadings were prepared by melt blending in a twin screw extruder. Scanning electron microscopy (SEM) observation on the fracture surfaces of the nanocomposites showed not only a uniform dispersion of AT-PU but also a strong interfacial adhesion with the matrix. Differential scanning calorimeter (DSC) and Thermogravimetric analyzer (TGA) were used to illustrate the influence of AT-PU particles on the thermal properties of the nylon 6/AT-PU nanocomposites. The results indicated that the addition of attapulgite probably induced the heterogeneous nucleation and was favorable for the formation of γ -crystalline form, and that the higher thermal stability was obtained for the composites.