Although briefly interrupted by the Zhou dynasty of Zetian Wuhou, Empress Wu, the Tang dynasty continued for nearly three hundred years both before and after the Zhou. How the Tang dynasty appraised the Zhou dynasty of Empress Wu was thus an important problem for the Tang. By examining the edicts of the Tang dynasty that listed previous emperors, it is possible to approach this problem based on the expressions used in the Tang court's own edicts. With the exception of edicts from the period prior to Gaozong's reign when the names of only one or two emperor's were listed, nine edicts from the Tang dynasty, which include edicts of general pardon, listed all previous emperors. They were: 1) the Edict Renewing the Reign to Guangzhai 改元光宅詔, 2) Pardon on the Renewal of the Reign to Zaichu 改元載初赦, 3) Pardon on the Accession of Zhongzhong 中宗即位赦, 4) Pardon of the Southern Outskirts in the Third Year of the Reign of Jinglong 景龍三年南郊赦, 5) Pardon of the Northern Outskirts of the First Year of the Taiji Reign 太極元年北郊赦, 6) Edict of the Feng Ritual at Taishan in 13th year of the Kaiyuan Era 開元十三年封泰山詔, 7) Prayer for the Feng Ritual in 13th year of the Kaiyuan Era 開元玉牒文, 8) Edict of Xuanzong on the Occasion of the Imperial Progress to Puanjun 玄宗幸普安郡制 9) Edict of the Ming Emperor [Xuanzong] Ordering the Accession of Suzong 明皇帝令肅宗即位詔. These edicts were issued in limited circumstances such as when Zetian Wuhou was clearly in the process of establishing the Zhou dynasty (edicts 1 and 2), the period of Empress Wu's decline and Zhongzong's rise (edict 3), that of the general pardons that were important ceremonial events for Zhongzong and Ruizong (edicts 4 and 5), through the period of Xuanzong's fengchan ceremony at the start of his reign (edicts 6 and 7), to the time of Xuanzong's abdication due to the turmoil of the An Shi revolt (edicts 8 and 9). Edicts that list all previous emperors were all issued in the mid-Tang when the dynasty was facing major political changes. Among these, praise for the achievements of Gaozu, Taizong, and Gaozong are prominent in 1) and 2); Zetian Wuhou is referred to as emperor in 3) and the suppression of the movement against Empress Wu is praised. In the periods of transition from Tang to Zhou and Zhou to Tang, there was no move to deny the achievements of the previous emperor, but the reverse, since by affirming them a peaceful political transition could be emphasized. Empress Wu was not referred to as emperor in 4) and 5), but 5) explained that her rule was the necessary politics of expediency, using the term congquan 從權. The characterization of the rule of Empress Wu as necessary expedient that is seen in the edicts of the Zhongzong and Ruizong reigns can be seen elsewhere. Necessary expediency, congquan, became the explanatory principle used by both Zhongzong and Ruizong for the Wuhou regime. Thus in 6) and 8) during the reign of Xuanzong, Empress Wu ceased to appear in the list of previous Tang emperors. From the succeeding reign of Suzong onward, previous emperors were represented by the number of their reign. But Empress Wu's reign was not included among those numbers. The existence of Zetian Wuhou was considered during the reigns of her true sons Zhongzong and Ruizong, but when it came to the reign of her grandson Xuanzong, there was a conscious effort to ignore her reign, which continued to the end of the Tang. In short, regarding the treatment of Empress Wu in the wording of edicts, the reign of Xuanzong can be understood as break with tradition. Moreover, the emperor is represented in many edicts by use of a posthumous name. Thus, when this problem is considered in the future, it will probably be necessary to pay further attention to posthumous names. At the same time, we need to be aware of the fact that in the Tang edicts the founder of the dynasty, Gaozu, was honored as Wu 武, and Taizong was accorded the name Wen 文.