A super-sensitive, high-specific immunoassay of tumor marker based on Surface Enhanced Raman Scattering (SERS) was developed with the sandwich-type immune structure consisted of Ag-covered polystyrene sphere (PS@Ag) probes and Ag-deposited Si pyramid array (Si@Ag) substrate. The PS@Ag immune probe was prepared by successively immobilizing 4-Mercaptobenzoic acid (4-MBA) and Anti-AFP antibodies on the surface of in-situ reduced PS@Ag nanoparticles. The Si pyramid array was fabricated using PS spheres as a template, combining with Langmiur-Bloggt method, reactive ion etching and wet chemical etching techniques. Then, Si @Ag immune substrate was prepared by successively depositing Ag film and immobilizing Anti-AFP antibodies on the surface of Si pyramid array. The results demonstrate that the constructed immunoassay platform exhibits high sensitivity with the limit of detection of 1.75 fg·mL－1 and wide linear range from 2 fg·mL－1 to 200 ng·mL－1. In addition, the detections of serum sample show the SERS-based platform is not only well-consistent with that of chemiluminescent immunoassay but also more sensitive, which could be potentially applied in the practical clinical diagnoses of cancer.