Why do ceremonies change? How do they change? Ritual innovation must come through replicating,expanding or restructuring established rites,and is not necessarily dominated by ideas or political aims.The changes in major sacrificial ceremonies,which occurred over more than a hundred years,from the middle years of Gaozong’ s reign to the later years of Xuanzong’ s reign,in fact took as its blueprint the first Tang fengshan ceremony(sacrificial worship of Heaven on Mount Tai) held in the first year of Qianfeng.With the change,in major sacrificial ceremonies,members of the royal family replaced high-ranking officials as acolytes or zhuji(助祭);the peixiang or ancestors worshipped in the sacrifice were worshipped together rather than one by one;and large-scale sacrificial ceremonies that represented a thorough break with tradition,such as Empress Wu Zetian’s Mingtang New Rites and Emperor Xuanzong’s Three New Major Rites,borrowed and expanded the composite structure established in the Fengshan ceremony.During this period,the major sacrificial ceremonies were undergoing progressive restructuring;the increase in imperial power was not the reason but the product of this change.