Spike is a protein in SARS CoV-2 that plays an important role in viral binding. Its Receptor Binding Domain (RBD) site attach to Angiotensin Converting Enzyme (ACE-2) on the host cell surface. Spike RBD is widely studied to be used as a sub-unit vaccine. In this study, we developed the RBD of spike protein that is expressed in CHOK-1 mammalian cell. The RBD was generated as a fusion protein with the Fc region of Human Immunoglobulin (RBD-IgG Fc) to improve its immunogenicity. The transient expression in CHOK-1 showed that the fusion RBD-IgG Fc was recognized by anti-RBD monoclonal antibody and antihuman IgG. The limiting dilution for single clone selection using geneticin as a selectable marker resulted in two clones that produced RBD-IgG Fc protein. To conclude, the RBD-IgG Fc fusion protein was successfully expressed in CHOK-1 cell line as a transient and stable expression. [ABSTRACT FROM AUTHOR]