Silver nanowire (Ag NWs) have been successfully synthesized by thermally assisted photoreduction (TAP) of aqueous silver nitrate (AgNO 3) solution on titanium dioxide (TiO 2) films . Nevertheless, the nucleation and nucleation and growth of the Ag NWs on TiO 2 substrate were monitored in detail by in-situ synchrotron radiation x-ray diffraction (SR-XRD). As-annealed TiO 2 film, followed by heating from 60 to 300°C, shows strong in-situ SR-XRD ratios of Ag(220)/Ag(200) spectra, indicating the preferred growth direction of NWs toward <220>. The nano-Auger electron spectrum (AES) demonstrates that silver nano-particles could was locally at room temperature on as-annealed TiO 2, which was partially excited by blackbody radiation. These Ag clusters will act as nucleation site for Ag NWs. It implies that the homogeneity and amount of electrons on the TiO 2 surface and the accumulative direction of Ag atoms are the key points for Ag Nws synthesis.