The period from the Northern Dynasties to T'ang Dynasty was a time when Maitreya faith was the predominant cult. This study probes into this phenomenon by examining the Buddhist scriptures (the sutras),the iconographic features of Maitreya imagery, and the historical events, with an aim to have a better understanding of the developments and influences--especially on political activities--of the Maitreya cult during these several hundred years. We can see from the Chinese translations of the Buddhist scriptures that Maitreya is the simulation and idealization of the personality of Sakya, and that Cakravartin is a special case of good kings in the mundane world. People expected the eternity of the spirit of the Buddha Sakya, and the existence of a perfect political system. This is why the scripture about the coming of Maitreya into the mundane world attracted such serious attention, and why it was so prevalent. Maitreya and Cakravartin appeared in this world at the same time. Maitreya operates the fa-shen protection, the Cakravartin operates the sheng-shen protection. The combination of the two realized the celestial Pure Land (sukhavati), and saved all beings. The Emperors from North Wei to Tang took themselves as Buddha or Cakravartin, and combined the Emperors' laws with the laws of the Buddha, so that the regimes and the governments could be rationalized and authoritarian; Emperor Wen-cheng of North Wei, Emperor Wen of Sui and Empress Wu of T'ang were examples. But among the people, there were also rebels who took themselves as the new Buddha or the new Cakravartin, pursuing the Pure Land. Judging from the iconographs of Maitreya imagery of Sui and T'ang, the Maitreya faith in this period centered around returning to the heavenly paradise and coming into the celestial Pure Land. But comparatively speaking, the Buddha portraits of Maitreya in T'ang Dynasty outnumbered the Bodhisattva portraits of Maitreya in the same period. Also, in the ching pien hsiangs (narrative paintings based on sutras) of Maitreya imagery, those showing Maitreya's coming into the celestial Pure Land outnumbered those showing His returning to heaven. This fact also reflected the relative popularity of the faith of Maitreya's coming in civilian beliefs.