In order to investigate the biological characteristics changes of Streptococcus suis after being irradiated by 30 Gy, 50 Gy 12C6+ ion, Microbiological methods and Toxicology methods were used to detect hemolytic, antibiotic sensitivity of 18 kinds of antibiotics, biofilm formation ability, surface hydrophobic, and virulence of parent Streptococcus suis strain and mutant strain. Compared with the parent strains, the results showed that there was no significant difference in 30 Gy12 C6+ ion group in the aspect of hemolysis, antibiotic sensitivity, ability of biofilm formation, surface hydrophobicity and virulence (p≥0.05); the antibiotic sensitivity of Streptococcus to Trimesulf, Streptomycin, Trimethoprim, Gentamycin, Lincomycin in 50 Gy 12C6+ ion group was of significant difference (p≤0.05), but there was no significant difference in hemolytic, biological film forming ability, surface hydrophobicity and virulence (p≥0.05). In conclusion, there was no significant change in biological characteristics of Streptococcus suis after irradiation with 30 Gy 12C6+ ion, significant changes of the some antibiotic sensitivity were found in 50 Gy 12C6+ ion irradiation group, but different mutations change differently in sensitivity to different antibiotics.Cited