A new nanocomposite consisting of polyaniline (PANI), montmorillonite (MMT) and La3+ was developed via in-situ polymerization of aniline in the presence of MMT and La3+ through emulsion polymerization, and also a novel network structure consisting of nanowires had been shaped. The morphology and the chemical structure of the product were studied by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The thermal property was exmined by mean of gravimetric analysis (TGA). The results indicated that PANI/MMT/ La3+ namocomposite has formed nanowires with diameter about 5 nm. The novel network structure consisting of nanowires has been shaped and overlapped towards certain direction. The formation of this network structure reveals that PANI molecules have been successfully inserted into the interlayer of MMT. Meanwhile, this conductivity network is believed to lead to the great improvement of the electrical conductivity for the nanocomposites. The FT-IR spectra reveal that PANI is obtained via in situ polymerization of the aniline monomer and there is a strong interaction between PANI and MMT. From XRD analysis, it can be also seen that the PANI molecules had been successfully intercalated into the galleries of the MMT. Moreover, the arrangement of PANI is more ordered in PANI/MMT/La3+ nanocomposite than that of pure PANI. From TGA curves, it is apparent that the introduction of MMT and rare-earth ions (La3+) exhibited a beneficial effect on the thermal stability of pure PANI. This markedly enhanced thermal stability of the nanocomposites can be ascribed to the MMT nanolayers acting as barriers for the degradation of PANI in the interlayer spacings and the inorganic nanoparticles trammeled the movement of the PANI molecule chains. They make the thermal decomposition of the nanocomposites at a disadvantage. As a consequence, the needed energy of the thermal decomposition increased, the thermal stability of nanocomposite increased. The paper offers a novel PANI/MMT/La3+ nanowire composites.