Abstract: In the timber structure of ancient architecture, the Pu-pai Fang is widely arranged above the dovetail joint, forming reinforced dovetail joints with Pu-pai Fang. To obtain the aseismic performance of these joints at different degrees of looseness, a numerical analysis model is established following experimental tests, and the moment-rotation relationship formula of joints under the common changes of rotational degree, of horizontal and vertical displacement is derived. The influence of the "narrowing" angle, of the height, and of the friction coefficient on the joint bearing capacity is analyzed. The research results show that Pu-pai Fang can effectively increase the joint bearing capacity and reduce the degree of decrease in the bearing capacity with the increase of loosening amount. Among them, the ultimate bearing capacity can be increased by up to 68.71%. The established numerical model and the proposed moment-rotation relationship are in good agreement with the test results. As looseness increases, the amount of joint tenoning remains relatively unchanged, the pull-out ratio increases, leading to earlier attainment of the peak moment and subsequent descending behavior during upward loading. The bearing capacity of the joint decreases with the decrease in dovetail height, but the "narrowing" angle and the increase in friction coefficient can improve the bearing capacity of the joint during upward loading.