This study reports a double‐SERS satellite nanocomplex immunoassay that made of an Au–Ag dealloyed intra‐nanogap nanoflower (Au–Ag DINF) and Au magnetic nanoparticles (AuMNPs) for multicomponent PSA, and introduces a prostate Health index (PHI) assay for potential PCa screening, especially the patients with a tPSA level in “diagnostic gray zone”. The gene discussed is KLK3; the disease is posterior cortical atrophy.