Investigating　the　diffusion　behavior　of　binary　system　is　crucial　for　understanding　the　solid-state　diffusion　in　metallic　joints,　as　it　affects　the　interfacial　reaction　that　forms　intermetallic　components　(IMCs)　and　introduces　Kirkendall　voids　that　change　the　interfacial　microstructures.　In　this　study,　we　intuitively　investigated　the　interfacial　diffusion　behavior　of　Copper-Zinc　alloy　binary　interface　by　in　situ　transmission　electron　microscopy.　Our　findings　revealed　the　interfacial　diffusion　of　atoms,　the　growth　processes　of　intermetallic　phases,　and　the　evolution　of　the　Kirkendall　voids　during　thermal　diffusion.　We　observed　that　the　Zn　atoms　diffuse　rapidly　into　Cu　and　form　the　β　phase　at　the　onset　of　thermal　diffusion　at　200　℃.　Additionally,　with　increasing　temperature,　Cu　atoms　control　the　diffusion　and　the　formation　of　IMCs　due　to　their　higher　diffusion　coefficient　in　the　β　and　α　phases,　which　are　2.09　±　0.63　×　10−16　m2/s　at　250　℃　and　3.44　±　0.44　×　10−17　m2/s　at　300　℃,　respectively.　Furthermore,　we　found　that　the　interface　significantly　influences　the　interdiffusion　rates　of　the　IMCs　and　the　formation　of　Kirkendall　voids.　The　emergence　of　voids,　which　are　formed　at　the　initial　defective　site　and　the　IMC　layer　at　the　temperature　of　250　and　300　℃,　respectively,　leading　to　a　considerable　decrease　in　interdiffusion　at　the　binary　interface　of　two　orders　of　magnitude　in　comparison　to　unaffected　regions.　Moreover,　we　revealed　the　evolution　of　Kirkendall　void,　involving　the　formation　and　merging　of　holes,　as　well　as　the　gradual　thinning　of　atomic　layers　during　diffusion.　These　findings　are　essential　for　understanding　the　formation　and　evolution　of　IMCs　and　Kirkendall　void　in　binary　interfaces.　©　2023　Elsevier　B.V.