Three straight mortise-tenon joints in the base of melon-column were built to study their flexural behavior. The relationships of moment-rotation and failure modes were obtained through monotonic loading tests. The flexural behavior was simulated with finite element software. On the premise of some basic assumptions, the simplified mechanical model was built on the basis of experiments and numerical simulation. Research results show that the main damage type of joints is pulling out, and the resisting torque is mainly synthesized by the vertical load on the top of columns to rotation point. The moment-rotation curve can be simplified as a double broken line model.