A method for detecting the specificity of activated lymphocytes is provided. The present method can be used to detect the specificity of activated lymphocytes in recipients or patients after organ transplantation or being infected by pathogenic microorganism or vaccination. The establishment of the present invention can not only timely diagnose rejection in organ transplantation, but also provide guidance for rational medicament administration clinically. Furthermore, the present invention provides an accurate and quick method to detect infectious diseases. It will be significant to achieve the goals of early detection, early quarantine, early treatment, thereby reducing infection rate.