Abstract: Straight-tenon joints in ancient timber structures in southwestern China using column and tie construction are studied. Their mechanical behavior under low-cycle reversed loading is analyzed in detail, and an M-θ mechanical model considering the effect of pull-tenon capacity of joints is proposed. Experimental data are employed to validate the new mechanical model, and it demonstrates that results from the proposed model are in good agreement with those from experiments. Hence, the proposed mechanical model will definitely play a role in theoretical analyses of the seismic performance and reinforcement of Chinese ancient timber structures.