To investigate the distribution of ermB, ermA and mefA related to the erythromycin resistance gene, 32 drug-resistant Streptococcus suis type 2 isolates from different areas in Hebei province were studied to detect the ermB, ermA and mefA genes by PCR amplification. The results showed that among the drug-resistant 32 strains, 100% (32/32) amplified ermB gene, 21.88% (7/32) isolates contained ermA gene and none of these strains was positive for mefA gene. The researchers concluded that erythromycin resistance mechanism of pig Streptococcus isolates is mainly mediated by ermB gene. Nucleotide sequences comparison showed that the ermB gene of 20 strains and the nucleotide sequences in the GenBank had the sequence similarity of 95-100%. Compared with the reference sequence of AJ972604.1, Ser to Asn mutation at position 100 and Arg to His mutation at position 118 of ermB was mainly detected in the 20 strains. The researchers concluded that the ermB gene is relatively stable.