  Considering accretion onto a charged dilaton black hole, the fundamental
equations governing accretion, general analytic expressions for critical
points, critical velocity, critical speed of sound, and ultimately the mass
accretion rate are obtained. A new constraint on the dilation parameter coming
from string theory is found and the case for polytropic gas is delved into a
detailed discussion. It is found that the dialtion and the adiabatic index of
accreted material have deep effects on the accretion process.
