Polyolefin is inexpensive and has excellent physical properties, so it has been widely used in many fields such as the medical industry, construction, and food packaging. Nevertheless, polyolefins are regarded as a serious threat to the sustainability of human civilization because of environmental issues originating from mass production consuming fossil fuels, short usage cycles, and accumulation of waste polyolefins. The functionalization of polyolefins can provide a chemical strategy to enhance the sustainability of polyolefins and achieve a circular plastic economy. C-H functionalization chemistry has emerged as an elegant way of introducing functional groups into hydrocarbons.Some of those small molecule chemistries have been nicely applied to the post-polymerization functionalization of the polyolefins.This presentation will briefly review several recent representative examples, and present our recent work in the field of functional polyolefins and C-C bond cleavage chemistry.