Precise measurements on the growth rate and the hydrogen coverage on the growing surface of SiGe epitaxial film by silane/germane gas‐source molecular beam epitaxy (GSMBE) have been performed for the germane mixing ratio Xg of 0%–6%. For all Xg, the growth‐rate Arrhenius plot showed a distinct separation into the high‐temperature region with a lower activation energy and the low‐temperature region with a higher activation energy, similar to silane GSMBE. The growth rates in the low‐temperature region increased with Xg, while those in the high‐temperature region peaked at Xg=0.8% and decreased thereafter. As a result the transition temperature shifted towards lower temperatures. The activation energy in the low‐temperature region stayed almost unchanged or increased with Xg, which is quite contrary to the previous understandings and is thus discussed. A model is presented to describe the hydrogen desorption process from SiGe surfaces, which explains both the growth rate in the low‐temperature region and the temperature‐programed‐desorption (TPD) spectra obtained from the quenched growing surface. The role of Ge in the low‐temperature region is concluded to enhance processes involved in hydrogen desorption from Si atoms.