「望氣」是流行在秦漢時期的一種特殊現象，也是一種數術文化的信仰。「望氣者」是專門負責解釋「氣」的人，他們根據星氣之占來判斷人事的吉凶。秦漢時期的皇帝特別留意「天子氣」的現象，有時也以「望氣」的預言，作為改正朔、治水患、擇將領、興土木等決策的參考。東漢時代不再流行「天子氣」，「望氣」對於皇帝決策的影響也逐漸地式微。由於望氣預言的準確不一，隨著皇帝制度日趨鞏固，以及讖緯術的流行等因素，皆是「望氣」不復流行的主因。魏晉南北朝改朝換代頻繁，「天子氣」又流行一時，至隋唐時期以後，「望氣」的現象已不復載之正史。

＂Wang Qi＂ is that experts can forebode the good and/or ill omens from observing the changes of clouds in the sky. The Emperors in the Qin and Han Dynasties had the big trust in ＂Wang Qi＂, but the trust declined over time. It was prevalent again in Northern and Southern Dynasties but not in favor after Sui and Tang Dynasties. This article indicates that the waning ＂Wang Qi＂ was caused by the establishment of Monarchy and the raising of other numerologies.