The complex interactions between pathogen and the host cause humans' or animals' diseases. The interactions can result in different levels of the host's damage in the cells, tissues and organs. On the one hand, the pathogenicity and virulence of pathogenic bacteria are depended on the pathogen; on the other hand, they are associated with host factors and the interactions between pathogen and the host. Combining Streptococcus suis, in the aspects of adhesion and colonization, invasion, evasion and spread, bacterial strategies for overcoming the defense of host cells were summaried.