Abstract: γ-ray CT is one of the non-destructive technologies increasingly applied for radioactive waste assay in recent years. The radioactive sources in the target objects can be identified, quantitified and located by γ-ray CT, offering the bases for further disposal and management of the radioactive waste. In this paper, the application background of γ-ray CT for radioactive waste assay is briefly described, and the mathematical models, system designs of the technology are summarized, as well as its main performance indices and influencing factors. Furthermore, the research developments in key techniques about the algorithms and correction methods for radioactivity image reconstruction are introduced in detail. Finally, an outlook to future developments of the technology is given.