The nucleocapsid protein (NP) of hantavirus has been shown to be highly immunogenic in laboratory animals and humans, and it induces an early and long-lasting humoral immune response during hantavirus infection. In the present study, entire and three partially truncated open reading frames (ORF) of NP genes of Hantaan virus (HTNV) strain 76-118, a prototype of hantavirus, were amplified and then cloned in prokaryotic expression vectors. The recombinant whole NP and truncated NPs were expressed in Escherichia coli. In addition, their antigenic and biological activities were evaluated in an enzyme-linked immunosorbent assay (ELISA) for detection of a series of monoclonal antibodies (MAbs). Results showed that the expressed complete HTNV NP had a similar function as an authentic viral NP. The antigen sites on NP of hantavirus were mainly located in the N-terminus, and the region at 1-37 amino acid might be one important antigenic domain.