As a member of the 11S proteasome family, REGγ facilitates ubiquitin-independent protein degradation. Previous studies have largely concentrated on the effects of substrate protein degradation. However, the mechanism by which REGγ recognizes substrate proteins and the substrate selectivity of REGγ remained unclear. In this study, we discovered that the multiple substrate proteins of REGγ contain the RKRR conserved sequence. Subsequently, the degron of REGγ, RR(K)R(K)R, was ascertained through site mutation, BLI, and Cryo-EM analysis. Consequently, the recognition mechanism of REGγ and its substrate proteins was clarified. Simultaneously, the number of substrates was expanded through a combination of interactome and degron analysis. Moreover, we successfully constructed a targeted protein degradation system that utilizes the degron of REGγ, thereby providing a novel approach for targeted protein degradation.