The present invention relates to an N-benzyl tryptanthrin derivative, and preparation method and use thereof. The N-benzyl tryptanthrin derivative of the present invention is characterized in that the derivative has a structural general formula as represented by formula 1, wherein each group is defined as in the specification. The preparation method of the compound is simple, has mild conditions and high yield, and is suitable for industrial production. The N-benzyl tryptanthrin derivative has good indoleamine-2,3-dioxy-genase (IDO) inhibitory activity, and can be used for treating diseases having the pathological feature of IDO-mediated tryptophan metabolism.