Two protagonists Humboldt and Citrine in "Humboldt's gift" are characterized as restless even lunatic, for they are constantly or madly seeking something such as honor, power or intimate relationship something or other. This thesis intends to analyze Humboldt and Citrine's psychological troubles from the perspective of Lacan's theory and reveal that Humboldt and Citrine's psychological problem are rooted in the sense of fragmentation and lack caused by the separation from mother, and their struggle to seek safety and satisfaction is further destroyed by the industrialism and materialism prevalent in this novel.