The invention relates to a method for preparing a tetrahydrobenzo[b][1,8]naphthyridine derivative. Specifically, the invention provides the method for preparing the tetrahydrobenzo[b][1,8]naphthyridine derivative from an o-azidobenzaldehyde derivative and an aza 1,6-eneyne derivative under the catalysis of metal and acid. By adopting the method provided by the invention, a transition metal catalyst is used and the tetrahydrobenzo[b][1,8]naphthyridine derivative, which is difficult to obtain by other methods and has a multiplex-ring structure, is obtained by adopting simple and easy-to-obtain raw materials through simple operation steps.