SDRG rats are an immunodeficient model with both Il2rg and Rag2 genes knocked out. Research indicates that compared with rats with a single Il2rg or Rag2 gene knockout, rats with a dual knockout of Il2rg and Rag2 exhibit a more severe SCID phenotype. Compared to Il2rg and Rag2 double-knockout mice, Il2rg and Rag2 double-knockout rats show higher engraftment rates for human tumor cells or xenografts in the construction of CDX and PDX models, retaining better characteristics of primary tumors. Data suggest that SDRG rats, characterized by the complete absence of mature T cells, B cells, and circulating NK cells, can be widely applied in oncology and immunology research.