1. During the Tang and Song Dynasties, the bucket arch was integrated with the beam and the square (the square column-shaped wood connecting the two columns), which played a role in transferring the load of the beam to the columns, supporting the weight of the eaves and increasing the depth of the eaves.

2. The bucket arch in Ming and Qing Dynasties highlighted the direct combination of beams, columns and purlins, reduced the middle level of the bucket arch, and became the main decorative component between the column network and the roof truss, which simplified the structure, saved wood and achieved the effect of obtaining more building space.

3. The difference between them: (1) The buildings in Tang and Song Dynasties have obvious ridge curves, roof curves and cornice curves, which are dynamic; However, the ridge curve and roof curve of buildings in Ming and Qing dynasties are not obvious. (2) The roofs of buildings in the Tang and Song Dynasties accounted for a small proportion in the elevation height, and the eaves were far-reaching and light; However, in the Ming and Qing dynasties, the roof of the building accounted for a large proportion, and the eaves were small, which made it look dignified. (3) In the Tang and Song Dynasties, the function of bucket arch structure was distinct, and the number of bucket arches in each bay was small, but the scale of bucket arch members was large; During the Ming and Qing Dynasties, the function of the bucket arch structure was weakened and the decorative significance was enhanced. There are more bucket arches in the bay, but the size of the bucket arch assembly is reduced. (4) In the Tang and Song Dynasties, the eaves columns of buildings mostly had side feet, rising and falling, and there were many columns, but few in the Ming and Qing Dynasties. (5) The details of other components are quite different. For example, the moon lights were very common in the Tang and Song Dynasties, but they were rarely used in the Ming and Qing Dynasties. In the Tang and Song Dynasties, the cross-sections of columns were varied (such as polygons and circles), while in the Ming and Qing Dynasties, columns were the main ones. In the Tang and Song Dynasties, there were techniques such as crossing hands and supporting feet, which were rarely used in the Ming and Qing Dynasties. The height of a large square section was greater than its width in the Tang and Song Dynasties, and it was close to 1: 1 in the Ming and Qing Dynasties.