In order to explore the potential threats of overuse of antibiotics to the ecological environment and human health,the northern sewage treatment were studied in detail. While the residual concentration of erythromycin, the characteristics of resistant bacteria and resistant genes in wastewater treatment plants were detected, by the isolation of microorganisms and PCR. The results showed that erythromycin concentrations in the ranges of 22.8 ~ 86.9μg·L-1, and their respective removal efficiency was low in the range from 55.4% to 66.3%. The concentrations of residual erythromycin-resistant bacteria in influent and effluent were 6.9 ~ 8.4 × 105 and 2.8 ~ 4.5 × 105 CFU·mL-1 , respectively. Based on the correlation analyses, the proportion of single erythromycin resistant strain was 45.0% , double antibiotic resistant strain was 40.84% , and triple antibiotic resistant strain was 14.16% . The resistant bacteria also showed different resistance to 6 kinds of antibiotics. Additionally, all antagonistic resistance genes were detected in the range between 2.3 ~ 9.5 log(copies·L-1). One single-resistant strain could not be detected for ere A, ere b, mef A/mef E and erm B. Among the triple-resistant strains, 4 strains could not be detected for tet Q and 3 strains could not be detected for Sul 2. The results indicated that the erythromycin residue in sewage was high, and erythromycin-resistant bacteria had multiple resistances, which had an important influence on the evolution of resistant genes and had a corresponding relationship with antibiotic-resistant bacteria.