Poly[(octamethyltetrasilylene)methylene] was prepared by the Wurtz reaction of bis(chlorotetramethyldisilanyl)methane. The periodic structure with Si4C-type sequences was characterized by H-1-, C-13-, and Si-29-NNIR. An investigation of the UV absorption and photoluminescence properties of this polymer in solid-state film revealed the unique character of Si4C-type periodic polycarbosilane. The sigma-sigma* transition energy varied from 5.2 to 4.5 eV due to conformation. The strong Stokes shift (1.2 eV) indicated that the emission is due to a "self-trapped" exciton state, in which excitation is weakly delocalized in a skeleton with a nonvertical geometry.