Due　to　unique　framework　structures,　Prussian　blue　analogs　(PBAs)　have　long　been　of　considerable　interest　in　biosensing.　However,　the　predominantly　cubic　morphology　of　most　PBAs,　along　with　their　inherent　elemental　and　structural　limitations,　restricts　their　catalytic　performance　as　the　nanozymes.　Herein,　we　designed　a　dualmetal　CuFe/Fe　PBA　nanozyme　composite　(CuFe/Fe　DMPBA)　exhibiting　excellent　peroxidase　(POD)-like　activity.　The　synthesized　FePBA　was　prismatically　loaded　along　the　inner　core　CuFe　PBA　to　build　an　epitaxially　deposited　structure.　This　unique　architecture　resulted　in　a　substantial　enhancement　of　the　POD-like　activity　of　the　composite　nanozyme　compared　to　its　individual　components,　FePBA　and　CuFe　PBA.　Leveraging　the　superior　catalytic　performance　of　the　synthesized　CuFe/Fe　DMPBA,　we　further　developed　a　highly　sensitive　and　selective　colorimetric　immunoassay　platform　for　the　detection　of　human　epidermal　growth　factor　receptor　2　(HER2),　a　crucial　biomarker　of　cancer.　Under　optimized　conditions,　this　nanozyme-based　immunoassay　platform　achieved　a　limit　of　detection　(LOD)　of　0.007　ng　mL-　1　and　a　linear　range　from　0.01　to　10　ng　mL-　1　for　HER2　detection.　This　work　not　only　presents　a　novel　strategy　for　synthesizing　high-performance　PBA-based　nanozymes,　but　also　provides　insights　for　the　rational　design　and　application　of　PBA　materials　in　bioanalytical　sensing.