Abstract: To further clarify the molecular mechanism of Gymnocypris przewalskii in response to stress and explore gene functions, this study cloned DNAJC2, a gene encoding J domain, and analyzed the response patterns of its related genes to Cu²⁺ stress. The study found that the open reading frame of DNAJC2 was 1 866 bp, encoding 621 amino acids, the untranslated region of the 5′-UTR was 108 bp, and the untranslated region of the 3′-UTR was 130 bp. DNAJC2 was higher expressed in the livers, brains, and gills of G. przewalskii. Compared with the blank control group, with the increase of Cu²⁺ concentration and the prolongation of stress time, gene Grp78, ID1, and DNAJC2 were above regulated in gills and kidneys, while gene Hspa14, Hyou1, RARα, and XPC were down-regulated or up-regulated and then returned to normal levels. In the liver, gene Hspa14 and ID1 were above regulated to participate in the stress response, while gene Grp78, DNAJC2, CDK8, and XPC were up-regulated or down-regulated and then down-regulated or up-regulated. Gene Hyou1 and RARα participated in stress response in an up-regulated way at low concentration, but down-regulated and then up-regulated at high concentration. These results indicated that gene Hspa14, Grp78, ID1, and DNAJC2 were involved in the biological process of exogenous stress and the cellular detoxification of heavy metals, and exogenous Cu²⁺ stress could affect the transcription of target genes and protein synthesis regulated by Hyou1, CDK8, RARα, and XPC.