In this article, the author tried to reconstruct the notion of henology in the text of French psychoanalyst Jacques Lacan. In 1970s, Lacan shifted his theoretical standpoint from "the Other" to "the One, " and corresponding to this shift, his clinical theory shifted from "the Symptom" to "the sinthome." The author investigated the roots of the henology in Lacan's text, and pointed out that from his early writings in 1950s, Lacan used the notion of "sign, " "trace, " which were supposed to be different from his famous notion "signifiant." In early and middle period, Lacan tried to dialectize this trace, and developed the dialect between the subject of the signifier and the subject of the enjoyment. But late Lacan tried to condense these element in relying on henological way of thinking, which was under the influence of one of his master, Étienne Gilson. The author concluded that this shift was the key for understanding of Lacan's notion, sinthome.