Abstract: In view of the status that the dynamic property of the roof-beams has been researched very little in the present research field of ancient timber structure, the palace timber structure is taken as the study object, establishing its roof-beams layer model according to the structural requirements of the annotation of Ying-tsao fa-shih. By the analysis of the dynamic properties, it obtained the structural dynamic characteristics and the maximal response of its displacement and acceleration under different conditions, and got the seismic amplification coefficient of the beams layer. Research shows that the first frequency of roof model is 1.486 Hz; the nature frequency of the roof model is much bigger than that of the whole structure of shaking table test; the maximal displacement value of beam layer increases with the earthquake and model height; the shock absorption effect of semi-rigid connection Sun-Mao in major earthquake (400gal) is better than that in moderate earthquake (220gal)and minor earthquake (110gal); the interlayer seismic amplification coefficient value lies in 1 or so; the seismic amplification coefficient between roof layer and arch shop lies in 0.9 around.