Proteins play important roles in biological and cellular processes. The levels of proteins can be useful biomarkers for cellular events or disease diagnosis， thus the method for sensitive and selective detection of proteins is imperative to proteins express， study， and clinical diagnosis. Herein， we report a "signal-on" platform for the assay of protein based on binding-induced strategy and photoinduced electron transfer between Ag nanoclusters and split G-quadruplex-hemin complexes. By using biotin as the affinity ligand， this simple protocol could sensitively detect streptavidin with a detection limit down to 10 pM. With the use of an antibody as the affinity ligand， a method for homogeneous fluorescence detection of Prostate Specific Antigen (PSA) was also proposed with a detection limit of 10 pM. The one-step and wash-free assay showed good selectivity. Its high sensitivity， acceptable accuracy， and satisfactory versatility of analytes led to various applications in bioanalysis.