北宋神宗以降的中樞體制，一直處在變化當中。先是熙寧年間的制度調整；接著是元豐官制改革，中書門下體制改為三省制；元祐時期又變整齊的元豐三省制，實現了三省同取旨、共聚議，還設立了平章軍國（重）事。作為當時整個官制變化的一部分，從制度演變的理路而言，這些變化遠承唐中後期以來的官制問題，是對「官失其守」現象的回應與再調適。但是，制度上轉承的時機與方式，實深受時政的影響，本文即試圖探討熙寧、元豐、元祐年間政治形勢變動與中樞體制變化之間的關聯。從中可以看到，時人對於制度調整並沒有一套一以貫之的思路；而是隨著不同時期面臨的特殊政治問題，藉著政策、人事變化的契機，塑造著各具特色的中樞體制。

The policy-making system of the Northern Song 北宋 dynasty constantly changed after Emperor Shenzong 神宗 (r. 1068-1086) ascended the throne. Since the middle of the Tang dynasty (618-907), the commission of a specific official had been often not necessarily indicated by the title of his administrative office. The institutional reforms in the middle of the Song were aimed at solving this problem. This paper argues that instead of drawing up a consistent plan to restructure the policy-making system as part of the reforms, Song authorities established different systems to adjust to the changing political situation under the reigns of Emperor Shenzong and Empress Dowager Gao 高太皇太后 as regent (1086-1093).