In order to understand the biol. characteristics of Streptococcus suis serotype 9 strains (KQ-1 and KQ-2), the identification of strains and their virulence genes, drawing of growth curves, mouse′s pathogenicity test were conducted. Those two strains were identified by Gram staining and PCR, then the primers of the main virulence genes (mrp, epf, sly, gadph, orf2, fbps, 89k) of S. suis were used to identify the virulence genes of the two strains. The two strains were cultured in TSB medium (containing 10% newborn calf serum), and their growth curves were drawn to get a preliminary understanding of the growth characteristics of the two strains. 45 Healthy Kunming rats were injected with two strains of bacteria for the pathogenicity test to understand their pathogenicity. The results showed that the Gram staining results of KQ-1 strain and KQ-2 strain were pos., they were identified as S. suis serotype 9 strains by PCR identification. The bacterial liquid d. of the two strains both reached the peak at 6 h when cultured at 37 °C. The results of virulence factors of the two strains showed that the genotype of KQ-1 strain was mrp+/epf-/sly+/gadph+/orf2-/fbps-/89k-, while that of KQ-2 strain was mrp-/epf-/sly-/gadph+/orf2+/fbps-/89k-. The results of pathogenicity test on mice show that the two strains are highly virulent.