In this study, five fragments of recombinant subunit Pasteurella multocida toxin (PMT) were constructed. Only pET28a-N1518 and pET28b-C2115 could be expressed efficiently in Escherichia coli. The molecular weight of the fusion proteins was 57 kDa and 78 kDa .Western blot confirmed that the two proteins could specifically react with antiserum against Pasteurella multocida toxin. No mice died after the intraperitoneal administration of these two proteins with the dose of 200 microg per mouse, but Vero cell was pathologically changed after administration of 896ng/mL rPMT-N. The fusion protein of rPMT-N and rPMT-C was purified, and emulsified with Freund's adjuvant in equal volumes to get subunit vaccine. Groups of Kunming mice were immunized subcutaneously twice at interval of two weeks. All mice were challenged intraperitoneally with 8.2 x 10(5) CFU HN-13 strain of T+Pm. The protection efficiency of rPMT-N, rPMT-C and crude PMT against HN-13 strain were 90%, 50% and 80%, respectively. The data revealed that the fusion protein of rPMT-N had immunogenicity and potential for developing a subunit vaccine against PAR in pigs.