With the development of molecular biology, more and more kinds of molecular libraries have been applied in the research of serodiagnostic reagents for infectious diseases. The molecular library technology has special values compared with conventional techniques for serodiagnostic screening of antigens, especially when the pathogens are difficult to culture artificially or the specific antigen purification is hard. In the present paper the application of DNA library, phage display random peptide library, phage antibody library, etc. in the research of serodiagnostic reagents and their special values were reviewed.