Ocular surface diseases are common diseases in ophthalmology.It is difficult for clinicians to make early and accurate diagnosis based on symptoms, signs and serologic examination.Compared with the blood test, the tear test can reflect the condition of the local ocular surface and it has the characteristics of being non-invasive, having high diagnostic accuracy and fast diagnostic speed.Tear detection uses modern detection techniques such as polymerase chain reaction, enzyme-linked immunosorbent assay, gene chip and protein chip to detect the pathogen and immune components in tear, including microbial nucleic acid, tear antibody (IgM, IgG, IgE, IgA, antinuclear antibody, etc.) and cytokines (interleukin, tumor necrosis factor, interference factor, transforming growth factor, epidermal growth factor, etc.). Tear detection provides information about the pathogen infection and immune response on the ocular surface.At present, a large number of domestic and foreign tear detection studies show that there are certain regular changes in tear composition, not only in ocular surface diseases, uveitis, fundus diseases, thyroid related ophthalmopathy, but even in systemic diseases such as diabetes, hepatitis B, acquired immune deficiency syndrome etc.In addition, the research of tear pathogen and immune components is of great significance to study the cause, biochemical and immune process, treatment of diseases.In this paper, the latest research progress of tear collection, the clinical significance of tear pathogen and immune components and the characteristics of tear in various diseases was summarized and analyzed to provide reference for clinical practice.