宗教祭祀於中國古代是大事，歷代君主莫不重視，各王朝不但制定祀典，祭祀名山大川、先聖先賢，更積極取締不在祀典內的祠祀。唐朝亦是如此。依《唐六典》所載，唐朝設有祠部郎中管理有關祭祀、卜筮、祠祀等事宜，而祀典標準，大多依照《禮記•王制》所定的準則，不過於祭祀器物與樣式方面有所更動。又唐朝的祀典分成大祀、中祀和小祀，依不同等級而有主祭和祭器方面的差異。所有的祠祀，在祀典內的稱為“正祀”，祀典外的稱為“淫祀”。法律規定的有關條例，如唐律和唐令，也是按照祀典等級而定訂懲罰標準。對於淫祀，官方大多採取毀祀的作法，有名的有狄仁傑和李德裕在江南的廢祀活動。他們大致上堅守“祀典”的準則，但是，兼顧地方民情和觀念變遷，各自在取締標準上富有彈性。淫祀的附屬，“左道”，也是官方注意的抵制對象，凡是僧俗往來過甚、卜筮惑人或僧道斂財，凡可能危及政權者，都在禁止之列。玄宗朝為此曾多次下詔禁止。

Since the ancient times, worship had been a major issue in China. Every dynasty not only instituted laws regarding rituals that were dedicated to sages and the virtuous and to the famous mountains and great rivers, but also strived to wipe out illegal worships. The Tang Dynasty was no exception. According to Tang liu dian, the government established an institute to manage religious rituals. The religious regulation in the Tang Dynasty mostly originated from The Book of Rites, yet, the government made a few alternations regarding ritual appliances. In addition, the government divided its religious rituals into three levels, and in accordance with the different levels stipulating in the law, there were also differences of the chief celebrants and ritual appliances. The rituals and worships which were specified in The Book of Rites were recognized as zhengsi (legal sacrifice or proper sacrifice, 正祀) by the government. Otherwise, it was categorized as yinsi (illegal sacrifice or improper sacrifice, 淫祀). The Tang dynasty also made legislation in accordance with The Book of Rites, as we can see in Tang lu (唐律) and Tang ling (唐令). In general, the Tang government would eliminate illegal sacrifices. The most famous campaigns of destroying illegal sacrifices were led by Di Renjie (狄仁傑) and Li Deyu (李德裕) in Jiangnan region. In launching the campaigns, these two eminent officials referred to the regulations in The Book of Rites, and considered local customs as well. Besides the rituals which were not stipulated in The Book of Rites, the religious worships that were regarded as threats to monarchs were forbidden by the government. For example, Tang Xuan Zong (唐玄宗) issued some edicts to regulate the relationship between clergy and the populace, to prohibit the use of witchcraft and illegal accumulation of wealth by clergy.