Objective To analyze the antimicrobial susceptibility, molecular types, serotypes, virulence factors and resistance mechanisms of Streptococcus agalactiae (S. agalactiae) isolated from pregnant women with advanced maternal age in Tangshan City, and provide basic data for the treatment, prevention and control of S. agalactiae infection. Methods 42 strains of S. agalactiae isolated from pregnant women with advanced maternal age in North China University of Science and Technology Affiliated Hospital as well as Tangshan Maternal and Child Health Hospital were collected. Detection of antimicrobial susceptibility and whole genome sequencing of 13 antimicrobial agents were performed. Results The percentage of tetracycline, erythromycin, levofloxacin, and chloramphenicol concurrently resistant strains was 7.1%, 35.7% of the strains presented multidrug resistance to erythromycin, clindamycin, and levofloxacin. The carriage rates of resistance genes ermB and tetM were 66.7% and 47.6%, respectively. 29 strains (69.0%) exhibited mutations in both gyrA and parC fluoroquinolone resistance determinants. 42 strains of S. agalactiae belonged to 4 serotypes, namely ⅠB (35.7%), Ⅲ (33.3%), Ⅴ (26.2%), and ⅠA (4.8%); and 11 sequence types (STs), with the highest proportion being ST10 (35.7%) and ST19 (31.0%); as well as 6 clonal complexes (CCs), among which CC19 (42.9%) and CC12 (35.7%) had the highest proportion. All S. agalactiae carried virulence factor-encoding genes of cfb, cylE, and pavA. Conclusion The molecular types and serotypes of S. agalactiae carried by pregnant women with advanced maternal age in Tangshan City pre-sent polymorphism, with obvious multidrug resistance, and carry multiple types of drug resistance genes and virulence genes.