This article starts with the death of Yuan An, the "heavy minister of the country" in the Western Han Dynasty, to an assassin, and then analyzes the tonality of the five assassins in "The Biography of the Assassin". In Sima Qian's view, the "Assassin" has considerable political height and historical value. We discovered the practical significance of the "Assassin" and understood why he values the Assassin so much. But what are the similarities and differences between assassins, knights, and killers? Can the "Assassin" give full play to its effectiveness in upholding justice and solving problems positively for the safety of the country? It is worth exploring in depth.