Abstract: Indoleamine 2,3-dioxygenase 1 (IDO1) is a key enzyme in the human tryptophan metabolism pathway, which can mediate tumor immune response. An IDO1 inhibitor would be a potential cancer immunotherapy drug. Based on the recently reported crystal of an IDO1 protein-inhibitor complex (PDBID:6AZV), the structure of reported inhibitor, and by analyzing the interaction mode between the inhibitor and IDO1, new inhibitor molecules were designed and synthesized. All structures were confirmed by spectral data. Preliminary activity studies showed that compounds containing an azabiphenyl tetrazole structure (B1 and B2) and biphenyl compounds containing a sulfonamide structure (D1, D2 and D3) had excellent inhibitory activity of IDO1 at the enzyme and cell level, and were comparable or even better than the control drug INCB24360.