The present invention provides an application of N-benzyl tryptanthrin derivative as tryptophan dioxygenase (TDO) inhibitor, and more specifically an application of N-benzyl tryptanthrin derivative or a pharmaceutically acceptable salt thereof. Said derivative has a structural general formula as represented by formula 1, wherein each group is defined as in the specification. The derivative of the present invention has a good TDO inhibiting activity and can be used to prepare a treatment for diseases associated with TDO activity and expression.
