When the samples were detected by SIgA-ELISA and IgG-ELISA, 138 of 260 swab samples were detected as M.hyopneumoniae SIgA antibody positive and 122 swab samples as antibody negative by the SIgA-ELISA at a cutoff of 0.107, while 162 of 260 serum samples were judged as M. hyopneumoniae IgG antibody positive and 98 serum samples as antibody negative by the commercial M.hyopneumoniae ELISA kit (IgG-ELISA).