清儒王夫之在《讀通鑑論》論唐宣宗毀壞唐室：「唐之亡，實宣宗亡之」，評價與《舊唐書》讚美宣宗「器識深遠……賢能效用」、《資治通鑑》稱頌之「明察沈斷」，實有天壤之別。宣宗究竟是明君，或應背負亡唐之匪名，本文無意從宣宗本人論斷其是非功過。《新唐書．百官志》稱「宰相」之職是「佐天子總百官、治萬事」，治亂興衰，宰相實難脫其責。而選擇宰相的決定權終究還是在天子手中，故本文擬從輔佐天子治國的宰相表現，看唐宣宗時代的政局及其影響。 正文略分五段，首由《新唐書．宰相表》配合《舊唐書．宣宗紀》合觀，合計宣宗在位共十三年五個月，期間所任、免的市相約有廿二位。除開前帝武宗倚重之李德裕在宣宗即位後首先遭紐，堪稱政局交替間的大事，值得重視應外，再由其中檢索出實際任事的代表性人物計白敏中、崔鉉、令狐綯、魏謨等人，就其出身、性格及政治表現，一一加以討論。 由宣宗所倚重的幾位宰相觀之，內亂外患危機處理不當，最後終於使更大規模的民變在宣宗晚年後爆發，亡唐之罪，白敏中、崔鉉、令狐綯等人皆難亂其咎。

　　　　　There are two extremely different views on Hisotriographical evaluation on Tang Hsuan-tsung (Li Yi). Some praised him as a brilliant emperor who can compare to Tang Tai-tsung, on the other hand, some blamed he to be reasonable for the fall of Tang dynasty. This essay is not going to evaluate Hsuan-tsung from himself, but from his ministers performance. As we all know, Minister’s duty was to help emperor to run the government, rule his country. Therefore, thru Ministers performance, no matter from their personality, or political capability…, we can judge whether Hsuan-tsung choose the right ones. The very first thing that he did, after Li yi became the emperor “Hsuan-tsung”, was to expelled minister Li Te-yu (李德裕). Few days later, he choose Bai Minchung (白敏中) to help him. As we can see, Bai Min-chung, later on, as well as Tsuay Hsuan (崔鉉), Ling Hu-tau (令狐綯), the three were the famous and real ministers thru the whole Tang Hsuan-tsung period. Therefore, we choose them to be study cases. As a result, we found that during late Hsuan-tsung period, his minister’s crisis dealing was inappropriate, frequent rebellions slowly converted the provinces into autonomous kingdoms under the control of warlords. Hsuan-tsung and his ministers were all to be blamed.