A　label-free　optical　sandwich　immunoassay　sensor,　utilizing　weak　value　amplification　and　total　internal　reflection,　was　devised　for　real-time,　high-sensitivity　analysis　and　detection　of　low-concentration　targets.　3D　printed　channels　and　sodium　chloride　solution　were　employed　to　ensure　reproducibility,　reliability,　and　stability　of　the　measurements　for　calibration.　The　sandwich　structure　demonstrated　enhanced　responsiveness　in　the　proposed　optical　biosensor　through　a　comparative　analysis　of　the　direct　assay　and　sandwich　assay　for　detecting　alpha-fetoprotein　(AFP)　at　the　same　concentration.　By　optimizing　the　binding　sequences　of　the　coating　antibody,　target,　and　detection　antibody　in　the　sandwich　method,　a　more　suitable　sandwich　sensing　approach　based　on　weak　value　amplification　was　achieved.　With　this　approach,　the　limit　of　detection　(LOD)　of　6.29　ng/mL　(pM　level)　for　AFP　in　PBS　solution　was　achieved.　AFP　testing　and　regeneration　experiments　in　human　serum　have　proved　the　feasibility　of　our　methods　in　detecting　complex　samples　and　the　reusability　of　sensing　chips.　Additionally,　the　method　demonstrated　excellent　selectivity　for　unpaired　antigens.　The　efficacy　of　this　methodology　was　evaluated　by　simultaneously　detecting　AFP,　carcinoembryonic　antigen　(CEA),　and　CA15-3　on　a　singular　sensor　chip.　In　conclusion,　the　label-free　sandwich　immunoassay　sensing　scheme　holds　promise　for　advancing　the　proposed　optical　sensors　based　on　weak　value　amplification　in　early　diagnosis　and　prevention　applications.　Compared　to　other　biomarker　detection　methods,　it　will　be　easier　to　promote　in　practical　applications.