Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae(GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the ?rst time in China, to characterize their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ?ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, holding36.9%(62/168), 37.5%(63/168) and 19.6%(33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia(95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. Ia initially occurred in 2009, it shoot up to 32.1% in 2010,but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007–2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types(N, O,P and Q), were observed, in which B, D, F and G were the predominant types, holding 83.9%(141/168) of the total GBS strains. Ia corresponded to 11 PFGE types(A–H, N–P), in which type D predominated(51%). Ib represented 3 genotypes(I, J and Q) and III harbored only 2genotypes(N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years.Although Iastillpredominated, new rareserotypeIII alreadyoccurred in China. Previously, we reported 10 PEGE types of 85 tilapia Streptococcus agalactiae (GBS), which shifted from Streptococcus iniae in China, by using PEGE method. Presently, larger and more representative tilapia GBS were isolated, for the? Rst time in China, to characterize Their serotypes and genetic diversities more precisely than had done before. 168 GBS strains were distributed in ve ve provinces of China, in which Guangdong, Guangxi and Hainan were the major ones, with 36.9% (62/168), 37.5% (63) / 168) and 19.6% (33/168), respectively. Serotypes, Ia, Ib and III, were observed in these strains and the most predominant one was Ia (95.2%), which mainly distributed in Guangdong, Guangxi and Hainan. in 2007, but decreased to 16.1% in 2011 before went up to 45.2% in 2012. Ib sporadically occurred during2007-2011, III onlyoccurred in 2012. 14 different PFGE types, including 4 new types (N, O, P and Q), were observed, in which B, D, F and G were the pre The dominant types, holding 83.9% (141/168) of the total GBS strains. Ia corresponded to 11 PFGE types (A-H, N-P), of which type D predominated (51%). Ib represented 3 genotypes J and Q) and III harbored only 2 genotypes (N and F). Type N and Fsynchronously presented in Ia and III. In summary, the genetic diversity of tilapia GBS varied by serotypes and changed with geographical locations and years. Although Iastillpredominated, new rare type III alreadyoccurred in China.