Abstract: The existing analysis model for a common joint is not suitable for a dovetail mortise-tenon joint due to its unique construction features. The force mechanism of a dovetail mortise-tenon joint was investigated and the moment-rotation relationship was deduced according to the mechanical equilibrium and deformation coordination. A two-linear model defined with a yield point and an ultimate point was proposed based on the results of a low-cyclic reversed loading test, and the calculated method for the characteristic points are recommended. The results obtained by the calculated model agree well with the experimental results. They are usable for the protection and maintenance of ancient timber buildings.