Background　and　Objectives:　Targeted　drug　is　often　engulfed　and　cleared　by　the　reticuloen-dothelial　system　in　vivo,　resulting　in　reduced　treatment　efficacy.　This　study　aimed　to　explore　the　biodis-tribution　and　HER-2-targeted　antitumor　effects　of　trastuzumab-modified　gold　nanorods　(Tra-AuNRs)　in　a　gastric　cancer　animal　model.　Methods:　Gold　nanorods　were　synthesized　using　a　seed-mediated　growth　method,　and　then　subjected　to　trastuzumab-targeted　modification.　Elemental　analysis,　Fourier　transform　infrared　spectroscopy,　and　X-ray　photoelectron　spectroscopy　were　performed;　UV-visible　absorption　peak,　photothermal　effects,　morphology,　and　size　distribution　of　Tra-AuNRs　were　characterized.　The　targeted　killing　effect　of　Tra-AuNRs　on　gastric　cancer　cells　was　assessed　in　vitro.　Tra-AuNRs　were　injected　intravenously　and　intra-tumorally　into　gastric　cancer-bearing　nude　mice　in　vivo　and　their　distribution　was　detected.　Tumor　growth　inhibition　rate　and　tumor　apoptosis-related　protein　expression　were　compared　between　groups.　Results:　Tra-AuNRs　presented　a　relatively　uniform　morphology　with　an　average　particle　size　of　59.9　nm　and　a　longitudinal　plasmon　resonance　absorption　peak　of　790　nm.　The　targeted　killing　rate　of　gastric　cancer　cells　in　vitro　by　Tra-AuNRs　was　87.9%.　After　intravenous　injection,　Tra-AuNRs　were　mainly　distributed　in　the　liver,　tumor,　spleen,　and　lungs.　Comparatively,　Tra-AuNRs　were　mainly　distributed　in　the　tumor　when　intratumorally　injected,　with　a　tumor　concentration　of　6.42　µg/g　after　24　h.　The　tumor　growth　inhibition　rate　reached　78.3%　in　the　intratumoral　injection　group,　with　significantly　higher　BAX,　BAD,　and　CASPASE-3　expression　than　that　in　the　intravenous　injection　group.　Conclusion:　The　findings　suggest　that　Tra-AuNRs　can　be　used　for　HER-2-positive　gastric　cancer　treatment.　Intratumoral　injection　of　Tra-AuNRs　significantly　increased　the　local　tumor　drug　concentration　and　improved　the　molecular　targeted　antitumor　growth　effect　in　gastric　cancer-bearing　nude　mice.　©　2024　Bentham　Science　Publishers.