We previously suggested that the protein p40 encoded by Scylla serrata reovirus (SsRV) segments S9 is likely to represent a methyltransferase. In order to confirm the role of p40 in the SsRV replication, the open reading frame (ORF) of SsRV segments S9 was cloned into the pET 28a(+) expression vectors and introduced into E.coli BL21(DE3) by transformation. After induction, N-terminally 6×his-tagged p40 recombinant protein (rp40) with molecular mass of 46 ku were obtained. The rp40 protein was purified by Ni-NTA and used for immunization of BALB/c mice for monoclonal antibody (MAb) production. Western blot assay showed that two MAbs could specifically recognize the rp40 expressed in E.coli. This was the first report on the MAb production of SsRV protein.