The desorption rate of surface hydrogen in the SiGe gas-source molecular beam epitaxy (GSMBE) using Si2H6 and GeH4 has been investigated by thermal desorption spectroscopy. We have experimentally obtained variations of kinetic energy and frequency factor in the surface-hydrogen desorption as a function of Ge content in the grown film. The desorption of surface hydrogen is enhanced by Ge addition to the growing surface, where both the decrease of activation energy and the increase of frequency factor in the hydrogen desorption take place. We present a rate equation of surface-hydrogen desorption as a function of Ge concentration for calculating growth rate in the SiGe GSMBE.