In order to identify the prevalence and distribution of Streptococcus suis serotypeⅡ in the historically infected regions in Hainan Province，four counties/cities including Dongfang，Wenchang，Danzhou and Baisha were selected，and an serological investigation and a questionnaire survey were carried out in 29 farms/premises covering 9 small-medium scale farms and 20 free-range households. The results showed that 95 out of 307 serum samples were detected positive，with an individual positive rate of 30.94%（95/307），17 positive farms/premises were detected out with a population positive rate of 58.62%（17/29）. The population positive detection rate ranged from 28.57% to 85.71%，and the individual rate was in the range of 4.00% to 84.15%，both of which were obviously different in various counties/cities（P＜0.05）；the small-medium farms were with higher population positive detection rate（77.78%）than free-range households（50.00%），but with lower individual positive detection rate（28.29%）than free-range households（36.27%），both of which were obviously different（P＜0.05）. The bio-security status of the farms and households concerned was poor，in which，35.7% were freely accessed to，only 21.4% were equipped with disinfection facilities for vehicles，and only 21.4% farms regularly organized training. It was concluded that Streptococcus suis serotypeⅡ was widely spread in the historically infected regions in Hainan Province，with poor effect of prevention and control and high risk of spreading，especially in the epidemic regions and free-range households. It was suggested that government authorities should strengthen the prevention and control，improve technical training and guidance for breeding workers，and upgrade the bio-security level of farms/premises，so as to reduce any outbreak. In the study，feasible guidance was provided for the prevention and control of Streptococcus suis in Hainan Province in the future.