The development of the growth technology of Si/Ge superlattices and the discovery of luminesceilce of porous silicon give rise to intense interest of investiration on .the Si-based low-dimensional structuxe materials. This paper reviews recent progress in this field, including:electronic states and optical properties of Si/Ge superlattices, transport properties of modulatinn doped Si/Ge.Si1-x. heterojunctions, and luminescence mechanism of porous silicon, etc.