As the emergence of new pathogens and problems within traditional pathogen prevention and control, the drug-resistant bacteria is increased, the common infection pathogenic spectrum changes, new infectious diseases and susceptible populations are also increased constantly. At present, clinical microbiology laboratories that can quickly and accurately detect the pathogenic microorganisms and provide clinical drug sensitive test results plays critical and irreplaceable roles in the clinical diagnosis and treatment of infectious diseases. They become to be an important department of medical institutions at all levels to control infection. We summerize here the function of microbiology laboratories in the diagnosis and treatment of infectious diseases and in hospital infection control as follows.