The major objective of this work is to understand the effects of attapulgite (AT) on the mechanical properties of polyacrylonitrile (PAN)/AT nanocomposite film. The well dispersed but irregularly distributed AT nanoparticles in the matrix was observed by scanning electron microscopy (SEM) and UV-vis spectra. The mechanical properties were investigated by means of tensile tests and dynamic mechanical analyses (DMA). The results showed that the incorporation of AT significantly improved the tensile strength and modulus of the PAN matrix. The fracture morphologies analysis has further suggested that small amount of AT nanorods may slide and orient along the tensile direction, resulting in homogenous stress transfer, thus increase the toughness of the PAN. However, the nanorods network formed in high AT content sample probably hindered the deformation of the matrix and generated the stress concentration points, leading to the remarkable increase of embrittlement of the samples. Following this concept, the volume of the constrained polymer chains was also calculated with DMA data and showed the good correlation with conclusion drawn in the tensile tests.