Objective To construct plasmid co-expressing mGM-CS and nucleocapsid protein of SARS-COV and study the expression of plasmid in vitro. Methods The mGM-CSF and N DNA fragment were amplified by PCR and inserted into eukaryotic expression vector called pVAX1/ N-GM-CS. COS-7 cells was transfected with recombinant plasmid, the fusion protein was detected by immunocytochemistry and Western blot method.Results The fuse plasmid was confirmed by enzyme digestion and DNA sequence, the fuse protein was detected in COS-7 cells. Conclusion The recombinant eukaryotic expression plasmid has been constructed successfully, and the fuse protein can express in COS-7 cellls.