Using the methods of atomic force microscopy, X-ray diffraction and Fourier transform infrared spectroscopy, chemical etching of the (010) surface of flux-grown orthorhombic MoO3 (alpha -MoO3) Single crystals has been investigated in detail. The (010) surface was etched repeatedly in a 0.08 M NaOH aqueous solution, and its topographies were recorded to reveal the evolution patterns upon the etching time. It is found that the "molecular steps" at a height of a single double-layer of MoO3 (6.9 Angstrom, or 1/2 b(o)) can be generated on the surface of (010) in the basic solution. A "layer-by-layer" etching mechanism proposed previously has been confirmed in this model catalyst fabrication. The observed etch pit volumes and multiple-step formation have also been addressed. Although they are created at room temperature, the surface steps/edges are chemically and thermally stable in a common operating temperature range of 350-400 degreesC. The fabrication/modification of future catalysts via chemical etching is anticipated, since surface steps/edges are expected to be active sites in many heterogeneous catalytic reactions.