Ovarian and gastric cancers, representative of many solid tumors, remain among the most challenging malignancies to treat due to limited therapeutic options and poor outcomes at advanced stages. Although immunotherapies have revolutionized cancer treatment, their efficacy in solid tumors has been hindered by issues such as antigen heterogeneity and the immunosuppressive tumor microenvironment. This study presents the development and evaluation of third-generation chimeric antigen receptor T (CAR-T) cells targeting B7-H3, an immune checkpoint molecule widely overexpressed in solid tumors. The B7-H3 CAR-T cells exhibited robust and selective cytotoxicity against B7-H3-positive tumor cells, sparing normal tissues. In preclinical animal models, these cells significantly inhibited tumor growth, demonstrating higher targeting specificity and preferential accumulation in tumor sites. These results highlight B7-H3-targeted CAR-T cells as a potential breakthrough in immunotherapy for solid tumors, offering a foundation for future clinical trials to refine their safety and efficacy.