Choroidal thickness is susceptible to age, sex and hormone levels under normal physiological conditions.In addition, under pathological conditions, the choroid is also vulnerable to ocular and systemic inflammatory reactions, resulting in the corresponding vascular reactivity changes, so that hemodynamic disorders will occur.When the normal physiological function of choroid is disrupted, imaging examination will show abnormal choroidal thickness.Optical coherence tomography can directly measure the changes in choroidal thickness, and its non-invasive detection method is convenient for patient follow-up and provides the basis for evaluating the progression of the disease.In recent years, researchers in various fields have proposed that the changes in choroidal thickness can become a new potential inflammatory index to evaluate ocular inflammatory diseases and systemic inflammatory diseases.In the long-term chronic inflammatory reaction, such as recurrent uveitis, systemic lupus erythematosus, rheumatoid arthritis and other diseases, the choroidal thickness is significantly lower than the normal value.But in the acute inflammatory response, such as the acute phase of sympathetic ophthalmia and the acute phase of posterior scleritis, the choroidal thickness will increase significantly compared with the normal value, and with the control of the inflammatory response, the thickened choroid will also decrease.However, the changing pattern of choroidal thickness is not the same, for example, the choroid is thickened in keratoconus, diabetic retinopathy, ankylosing spondylitis and other chronic inflammatory reactions.This article reviews the changes in choroidal thickness in ocular and systemic inflammation and its potential as a marker of inflammation.