Photoinduced electron transfer (PET) has been used as reporter in the field of photoluminescence sensors and switches, and intermolecular PET is believed to be responsible for fluorescence quenching. Herein, the emissions of Tb-MOF can be quenched effectively by protamine based on PET. Compared with conventional electrostatic attraction mechanism, this approach suffers less interference from other charged substances and has a broader linear range of protamine from 3 to 5000ng/mL with limit of detection (LOD) 1.21ng/mL. Subsequently, the strong binding effect of protamine toward Hep ascribed to electrostatic attraction hinders the interaction between Tb-MOF and protamine, resulting in the high emissions of framework. The detection of Hep also shows a good linear range from 0.5 to 5M with LOD 0.27M. Finally, this novel probe is also successfully applied to the determination of protamine and Hep in human serum with satisfactory results.