Hantavirus (HV) infection leads to a kind of severe systematic syndrome, hemorrhagic fever with renal syndrome ( HFRS). Heat shock proteins (HSPs) can be used as adjuvants assisting soluble antigens to produce specific targets which can be attacked by cytotoxic T lymphocytes. For further research on HFRS vaccine, this study aimed to express Hantaan virus nucleocapsid protein (HTNV NP)-HSP70 fusion protein in COS-7 cells. First, an HTNV S gene encoding NP was amplified by PCR with a mutated termination code and cloned into eukaryotic expression vector pCDNA3.1(+), into which the full-length hsp70 gene had already been inserted, to form the S-hsp70 fusion expression vector pCDNA3.1(+)/S-hsp70. Then this recombinant plasmid was transfected into COS-7 cells by liposome, and eukaryotic expression of NP-HSP70 fusion protein was detected by immunocytochemistry and western blot. The results show that the eukaryotic expression vector pCDNA3.1(+)/S-hsp70 was successfully constructed and the NP-HSP70 fusion protein was effectively expressed in COS-7 cells. This study demonstrates that the NP-HSP70 fusion protein was expressed effectively from the pCDNA3.1(+)/S-hsp70 vector in a eukaryotic system and thus provides a basis for using this plasmid as a new DNA vaccine against HV infection.