Single Si(1-x)Ge(x) epilayer on Si buffer layer (~100nm) was grown by gas source molecular beam epitaxy (GS-­MBE) at 640℃. Samples were investigated by transmission electron microscopy. For all the samples investigated, the misfit dislocations were irregularly distributed along the [110] and [110] directions. As the Ge content, x, in Si(1-x)Ge(x)/Si epilayers (x≤0.15) increased, the distribution of dislocations changed from a 2 dimensional to a 3 dimensional network in both the epilayer and buffer-substrate. The majority of misfit dislocations in the Si(1-x)Ge(x)/Si(001) epilayers was of 60˚ type dislocations.