Recombinant human interferon-β (rhIFN-β)， a therapeutic protein， is produced using both prokaryotic and eukaryotic expression systems. However， instability of recombinant plasmid during cultivation of results in low yield of the recombinant proteins. In addition， use of antibiotics during the cultivation imposes a major concern. In this study， we have compared the expression yield of rhIFN-β in BL21 (DE3) and SE1 cells. Gene-encoding rhIFN-β was expressed in BL21 (DE3) and SE1 cells and the cultivation of recombinant cells was done in a laboratory scale bioreactor. Our results suggest that， compared to BL21(DE3) cells， the SE1 cells expressing rhIFN-β protein can be cultivated in the medium without antibiotic and provide increased stability of recombinant plasmid and higher expression yield of rhIFN-β protein. This system can be used for the production of rhIFN-β proteins for biomedical applications.