The pathogenesis of depressive disorder is complex. The disorder of Kynurenine pathway （KP） may be associated with the formation of depressive disorder. KP metabolites， such as kynurenic acid and quinolinic acid， have been confirmed to be closely related to the pathogenesis of depressive disorder. The study of metabolites in this pathway may provide objective diagnostic markers for the diagnosis of depressive disorder. This article reviews the research progress on the diagnosis and treatment of depressive disorder and KP metabolic disorder.