We have observed a conversion of step configuration of 3.5° miscut Si(001) surface after depositing several monolayers of Ge by using a scanning tunneling microscope. For a 3.5° miscut Si(001) surface, terraces are spaced by double‐atom height steps and all dimer rows, either on the upper terrace or on the lower terrace of a step, are normal to the step edge, defined as single‐domain (1×2) surface. After depositing 2 ML of Ge, the surface is still single domain, but dimer rows have changed their direction, running parallel to the step edge and single domain (2×1) appeared. The reason for such conversion is attributed to the strain that existed on the epilayer of Ge. ©1996 American Institute of Physics.