劉向經主《穀梁》；劉欽學尊《左傳》。然以《漢書‧五行志》考察，則二人皆以《洪範五行傳》解釋《春秋》災異，並各自著有《洪範五行傳論》，應屬以洪範五行傳學說宗之災異學者。本文主要在於比較向、歆父子《洪範五行傳論》在著作背景、內容體系、學術與政治態度等面向之異同。主要意見如下： 劉向著作乃對於董仲舒災異說之改造，除了參考先秦諸多典籍擴大採擇史事範圍之外，並以洪範五行傳學說取代了春秋公羊災異學說。劉欽則主要以引述《左傳》史事反駁前人對於災異推度的錯誤。 二人在《洪範五行傳論》內容體系之差異上，向、歆父子對於災異理論架構如五行五事的對應項目、災異項目與五行五事的對應關係，認定多有差距。此外，二人對於災異占候事件詮釋亦有不同。 劉向災異說與其他著作相似傾向匯整、承繼前人的傳統說法。而劉歆則勇於挑戰權威，因此說法多與傳統說法有別。反映在災異說上，劉歆旣不同於董仲舒、劉向強調上天示警的天人關係，亦不同京氏易學者擅長預言式的占候之術，反與天文曆法密切相關的明堂月令學說較為雷同。雖然，劉向、劉歆父子的《洪範五行傳》理論體系存在著許多歧異，但並不影響洪範五行傳學說的發展。

As scholars of jingxue (classical studies) Liu Xiang and his son Liu Xin displayed clear difference in their areas of specialty. However a close look based on the Hanshu (Book of Han) shows that they both explained the anomalies (zaiyi) in Cunqiu (Spring and Autumn Annals) by drawing upon the Hongfan wuxing zhuan. In fact, each of them wrote a treatise called Hongfan wuxing zhuan lun. This article explores the two Lius' versions of Hongfan wuxing zhuan lun and compares their theories of anomalies by calling attention to the specific backgrounds in which the two treatises were produced. It also examines the similarities and divergence between the two treatises in terms of their systematic contents and the scholarly, political attitudes they bore out.