符瑞、災異是天人相應思想中的兩個組成要件。符端的作用在證明政權的合理性，災異的作用在約束君或臣的濫權。兩晉時期符瑞、災異思想頗為盛行，當時對於符瑞的運用，有下列四種方式：一、用以合理化晉代政權的建立。二、用以合理化對政權的篡奪。三、用以合理化承繼帝位。四、用以合理化政權的永恒性。對於災異的處置與運用，財有下列三種方式：一、君主因災異下詔責己或責臣。二、臣因災異被策免或上疏引咎遜位。三、臣藉災異上疏諫君或責臣。 符瑞、災異思想在兩晉之所以仍具影響力，其原因有二、一是由於兩晉帝位的承繼常有不合於傳統的繼位方式，需要符瑞證明其合理性，二是當時道教、卜筮、占候等宗教、術數思想的盛行。

Fu-rui and Zai-yi are the two institutions of Tian-jen-xiang-ying (天人相應) related thoughts. The function of Fu-rui is to justify the political power, while the function of Zai-yi is to retrain the monarch and his subjects’ excessive power. During the two Jin Dynasties, Fu-rui and Zai-yi was very popular. At the time, for the application of Fu-rui, there were four forms: (1) To the establish reasonable Jin Dynasty’s power, (2)To reasonably wrest the political power. (3)To rationalize the heritance of purple. (4)To rationalize the immutability of political power. As for the treatment and application of Zai-yi, there were three ways: (1)The monarch blamed himself or his under subjects (officers) because of Zai-yi. (2)The official was relieved from his post or blamed himself and retired earlier because of Zai-yi. (3)The official wrote a letter to persuade the monarch or blamed himself. Why the Fu-rui and Zai-yi thoughts were so popular in the two Jin Dynasties, there were two reasons: (1) The heritance of purple in the two Jin Dynasties did not conformity with the traditional heritance way, and it was necessary to justify it with Fu-rui. (2)Taoism and divination were very popular at that time.