Abstract: The palace-style timber frame of Tang Dynasty has been standing up for a long period, and it has good seismic performance. The timber frame will rock and lift repeatedly under horizontal earthquake excitations, which is associated with energy conversion due to the relaxed constraint floating column foot joint and the big roof. Therefore, it is necessary to further reveal its seismic mechanism through energy analysis of the timber frame. The energy balance relationship of the rocking timber frame under earthquake actions was analyzed. The refined finite element model of a typical palace-style timber frame of Tang Dynasty was established and the dynamic time history analysis was carried out. The seismic mechanism was revealed through the analysis of energy composition and variation. The influences of seismic parameters, brackets complexes, column head and vertical load on the energy dissipation of the timber frame were studied. The results show that under the earthquake, the kinetic energy, gravity potential energy and elastic strain energy are continuously transformed in the process of rocking of timber frame, and the seismic energy is dissipated through damping, friction and plastic deformation. Due to the energy storage advantages of the 'large roof', the kinetic energy of the input structure is stored in the frame by being converted into gravitational potential energy, which reduces the damage of the component and strives for time to consume seismic energy. The magnitude of vertical load and the amplitude of seismic wave acceleration have great influences on the energy of the timber frame: the greater the two parameters are, the greater the total input energy and damping energy dissipation of the timber frame are.