Scanning tunneling microscopy (STM) and x_ray photoemission spectroscopy (XPS) studies of germanium growth on Ru(0001) were carried out. STM measurements showed a typical Stranski_Krastanov growth mode of Ge on Ru(0001), i.e. first atomic wetting layer is formed in the submololayer range, and the formation of islands on top of a flat first layer occurs for subsequent layers. XPS measurements showed a weak interaction between Ge and the substrate of Ru(0001). The Ru 3d5/2 and Ru 3d3/2 corelevels of Ru(0001) are located at 2798 and 2840 eV in binding energy respectively. Upon Ge growth, up to a thickniss of about 20 atomic layers, the Ru 3d corelevels shift downward in binding energy by an amount of about 02 eV，while the Ge 3d corelevel shift upward in binding energy from the Ge low coverage limit of 289 eV to 290 eV，with a relative change of 01 eV.