Tilapia samples were collected from five main tilapia farms in Guangdong. The characteristics of the isolates were determined by virulence gene detection, Multilocus Sequencing Type (MLST), and PulsedField Gel Electrophoresis (PFGE). The frequency of virulence gene in all isolates varied from 60.59% to 100%. Ten distribution patterns of virulence gene were identified, dltR-bca-sodA-spb1-cfb-bac (38.24%,65/170), dltr-bca-sodA-spb1-bac (23.53%，40/170), and dltr-bca-sodA-spb1-cfb-bac-scpB (22,35%,38/170) were the predominant patterns, followed by dltr-bca-sodA-spb1-bac-scpb (8.24%, 14/170) and dltr-bca-sodA-spb1 (4.71%, 8/170). The single allele was observed in each of seven loci, adhP（10）, pheS（1）, atr（2）, glnA（1）, sdhA（3）, glcK（2）, tkt（2）and result in unique ST 7 (Sequencing Type 7). One hundred and fortysix isolates were assigned to six clusters based on the PFGE results. The similarity between these clusters ranged from 86% to 100%. Cluster A (18), B (16), C (103) and D (7) were the predominant clusters, account for 98.63% of all isolates. Cluster A and C were distributed in all four areas, Cluster B were mainly isolated from Wuchuan, Maoming and Yangjiang, whereas Cluster D were isolated from Maoming, Zhuhai and Yangjiang. The unique clusters F and G were isolated from Maoming and Zhuhai, respectively. In addition, the clones in Clusters A--D isolated from different areas in Guangdong showed 100% similarity. High proportion of strains with virulence gene was observed in Streptococcus agalactiae strains isolated from tilapia farm in Guandong. All of isolates belonged to the unique ST7. The clones with 100% similarity were identified in different area suggesting the cross infection and transmission in Guangdong, China.