The invention relates to a primer combination capable of detecting three kinds of streptococcus simultaneously. The primer combination consists of upstream and downstream primers capable of detectingstreptococcus agalactiae, as shown in SEQ ID MO:1, 2, upstream and downstream primers capable of detecting streptococcus dysgalactiae, as shown in SEQ ID MO:3, 4, and upstsream and downstream primerscapable of detecting streptococcus iniae, as shown in SEQ ID MO:5, 6. A reagent kit consists of a DNA extraction reagent and a PCR reaction reagent, wherein the DNA extraction reagent consists of a TEbuffer solution, proteinase k, chloroform, isopropyl alcohol, ethanol and redistilled water, and the PCR reaction reagent contains a reaction buffer solution, dNTPs, DNA polymerase, the 6 primers anddeionized water. A method for detecting the three kinds of streptococcus simultaneously comprises the steps of extracting DNA in samples through the extraction reagent, performing PCR amplification on the DNA through the reaction reagent, and performing gel electrophoresis on amplification products. The three kinds of streptococcus can be detected simultaneously, detection is simple, quick, highin sensitivity and high in specificity, and the primer combination and the method can meet requirements for large-scale molecular epidemiology investigation and analysis of aquatic animals and qualitysafety detection of aquatic products.