Most porous silicon samples studied have been oxidized in various degrees. Oxidized porous silicon and the nanoscale silicon particles embedded oxidized silicon have similar structures and luminescence characteristics. Both of them consist of a great quantity of nanoscale silicon particles, each of which is surrounded by an oxidized silicon layer, and can be named as nanoscale silicon/oxidized silicon systems. They are the most strongly studied and very promising silicon-based luminescence materials. In this article, the photoluminescence mechanisms of the nanoscale silicon particles/oxidized silicon systems were summarized and discussed. The related research works finished by our group in Peking university were briefly introduced.