The aim of this study is to obtain the molecular characteristics of Streptococcus agalactiae (Group B Streptococcus, GBS) strains isolated from seven aquatic animals in China, and then analyze the epidemiology and transmission of GBS strains in these aquatic animals. In this study, a total of 10 GBS strains were isolated from seven aquatic animals. These isolates were analyzed by four typing methods: molecular serotype, MLST (Multilocus Sequence Typing), virulence genotype and prophage typing. In addition, the pathogenicity of GBS strains was evaluated by zebrafish. The ten GBS strains were divided into three types based on molecular serotype, namelyⅠa, Ⅰb and Ⅲ. The results of MLST indicated that serotypesⅠa, Ⅰb and Ⅲ were ST7, ST261 and ST739, respectively. The ten GBS strains were divided into three virulence genotypes (V1, V2 and V3) determined by PCR detection. The FWL1405 strain (Ⅲ-ST739) isolated from Hoplobatrachus chinensis carried 11 virulence genes (11/12, 91.7%), and the Ⅰa-ST7 GBS strains carried 10 virulence genes (10/12, 83.3%), and the Ⅰb-ST7 GBS strains were possessed of 7 virulence genes (7/12, 58.3%). Prophage typing showed that the ten GBS strains were divided into four types (P1, P2, P3 and P4), and the strains of P1 and P1 types belong to Ⅰa-ST7 GBS strains. These results revealed that GBS strains from seven hosts were divided into four genotypes, and the FWL1405 strain was the unique type: Ⅲ-ST739-V1-P3, determined by the previous four typing methods. However, tilapia GBS strains (LT-1, WC1535, WT1451 and WC15122) were divided into three genotypes:Ⅰa-ST7-V2-P1,Ⅰa-ST7-V2-P2 andⅠa-ST7-V3-P4. More important, the GBS strains isolated from Aristichthys nobilis, Aequidens rivulatus, and Oreochromis sp., have the same genotype:Ⅰa-ST7-V2-P2. The strains isolated from Trachinotus ovatus, Scortum barcoo, and Oreochromis sp., have the same genotype:Ⅰa-ST7-V2-P1. Furthermore, the same genotype of the GBS strains were found that isolated from Cirrhinus molitorella and Oreochromis sp.. Additionally, in this study, all the GBS strains have strong pathogenicity to zebrafish (Danio rerio). In conclusion, the genotypes of ten GBS strains were significantly different between amphibians (frog) and fishes. The possibility was little that GBS strains transmitted between amphibians and fishes. Notably, there were three genotypes of GBS strains from fishes, and the same genotype GBS strains were all found in tilapia. These results indicated that the possibility was great that GBS strains transmitted among these six species of fish, especially between tilapia and other fish species.