Silicon (Si)-molecular beam epitaxy (MBE) generated many micro structures such as steps or nuclei, these wall faces of which were directed to some specific crystal orientations in the horizontal plane. Namely, it was indicated that Si molecules were anisotropically grown along with atomic steps by MBE. In this present paper, the crystal anisotropy of epitaxial growth was carefully investigated. As it can be considered that the anisotropy originates in the dangling bond arrangement in the atomic step, these generated micro structures have been analyzed by a newly defined parameter, "anisotropic factor", as a function of dangling bonds density and their direction cosine in the atomic step. As a result of the analysis, it was clarified that the anisotropic factor became local minimum in these specific crystal orientations observed on generated micro structures. It seems that 2-dimensional nucleus or step composing micro structure tends to be surrounded by some atomic steps, these orientations of which have local minimum an isotropic factor. The growth rate of atomic step can be expressed by anisoptropic factor, namely, the lower anisoptropic factor make the growth rate of atomic step relatively slower. In addition to this, It was clarified that the anisotropy of epitaxial growth don't depend on the crystal structure of bulk but that of reconstructed surface.