In the present study, we prepared novel polyaniline supported W15O49 (PANI/W15O49) nanocomposite by in situ oxidative polymerisation method. We herein focused on enhancing the stability and the photocatalytic performance of W15O49. The prepared PANI/W15O49 was thoroughly characterized by FTIR, TEM, XRD, BET, UV-vis DRS and PL. The PANI support presented a great effect on the light harvesting and photo-charge transfer of the W15O49, and the optimum percentage of was found to be 10 wt%. As for treating Cr(VI), the effect of important water quality parameters (such as pH, ions, NOM, DO, temperature and SOAs) on photocatalytic performance was investigated under the visible light irradiation (lambda > 420 nm). SOAs were shown to exert a dramatic accelerating influence on Cr(VI) reduction in the system. The obtained 10%-PANI/W15O49 can completely catalytically reduce 1 mM Cr(VI) in the presence of tartaric acid (1:3) within 50 min. Meanwhile, it can be recycled at ten times without any loss of photocatalytic efficiency, indicating the high stability of the as-prepared photo catalyst. The results of the study demonstrate the potential of the new obtained photocatalyst in efficient utilization of solar energy for treating aqueous Cr(VI).