A suspected case of Streptococcus suis infection was detected in piglets in delivery room of a farm in Weifang city of Shandong province in October 2016. For accurate diagnosis and further prevention and control of Streptococcus suis disease，the bacterium in the case was isolated and identified by culturing，Gram's staining，biochemical testing，gene identification and animal experiment. The results showed that the case was an infection of the Streptococcus suis 2（SS2）. Then，the nasal swabs were collected from the delivery room，weaning swine house，fattening house and the mother feeding stalls. Genes of 16S RNA and cps2 were detected by PCR. The results indicated that only circulated SS2 in the delivery room，but not in the other houses.