Provided are : an oxadiazole derivative as shown in formula (1), or salts, esters, stereoisomers, tautomers, polymorphs, solvates, hydrates, metabolites or prodrugs thereof, or a mixture of said substances; a pharmaceutical composition comprising the oxadiazole derivative and a medicine case; the preparation method therefor; and the application thereof in the preparation of a drug for the prevention or treatment of disorders induced by indoleamine 2, 3-dioxygenase mediated immunosuppression.