Objective · To obtain high purity rat α2 macroglobulin (Rα2M) and screen the protein crystals in order to collect high-resolution diffraction data for subsequent structural biology research. Methods · The gene for encoding Rα2M was cloned into the eukaryotic expression vector pCEP4. Recombinant Rα2M was expressed in HEK293EBNA cells using PEI-mediated transient transfection method. Rα2M was purified with anion exchange column and nickel affinity chromatography and purified Rα2M was crystallized, screened, and optimized. Results · The recombinant full length Rα2M protein with a relative molecular mass of about 180 000 was obtained after purification, as well as small and large fragments after slicing. Rα2M protein crystals were obtained after crystallization screening and optimization. Conclusion · The Rα2M crystals that can be used for crystal diffraction were obtained. This work lays a foundation for subsequent elucidation of the crystal structure of Rα2m.