Monodisperse　TiO2-xNx　nanocrystals　were　successfully　synthesized　in　Nafion　membrane　at　low　temperature　in　a　convenient　way.　Several　characterization　techniques,　X-ray　diffraction　(XRD),　UV-vis　absorption　spectra　and　X-Ray　Photoelectron　Spectroscopy　(XPS)　are　combined　in　order　to　determine　the　crystal　phase,　grain　size,　optical　absorption,　and　state　of　the　resultant　oxynitride　chemical　bonding.　The　photocatalytic　activity　and　stability　of　the　homogeneously　dispersed　TiO2-xNx　nanocrystals　embedded　in　Nafion　membrane　were　evaluated　through　a　study　of　the　decomposition　of　Methylene　Blue　under　visible　light　irradiation.　It　was　found　that　the　photocatalytic　activity　of　the　TiO2-xNx　nanocrystals　can　be　enhanced　efficiently　by　re-nitridation.　Also,　the　form　of　Nafion,　acidic　or　salt,　affected　photocatalytic　activity.