In this article, as-evaporated and annealed samples of Ge/Au, Ge/Ag bilayer films and Ge-Au, Ge-Ag alloy films were investigated by TEM. In situ observations of Ge/ polyerystalline Au (p-Au) and Ge/p-Ag films during heating were also made by TEM. It is found that crystallization temperature Tc of amorphous Ge (a-Ge) in a-Ge/p-Au is much lower than Tc of a-Ge/monocrystalline Au (m-Au). It is shown that the boundary triple points and other interface defects of p-Au films are the favourable nucleating positions for a-Ge crystallization in bilayer films. Tc of a-Ge in the condensation regions of Ge/p-Au films (≈100℃) is lower than Tc (≈150℃) in the noncondensa-tion regions. There are some large Ge grains in the condensation regions because of the effect of favourable crystallization in local regions. Tc of a-Ge in a-Ge/p-Ag and a-Ge/ m-Ag films is about 280℃. Tc of alloy films is higher than that of correlative bilayer films when metallic content in alloy film is low (CAu Agc of alloy films is lower than that of bilayer films when metallic content is relatively high. It is because of smpersaturation metallic atoms which reduce the crystallization potential barrier of a-Ge significantly.