Drug induced long QT syndrome is a high risk event in clinic， which mainly results from their high affinity to the Human Ether-a-go-go-Related Gene (hERG) potassium channel. Therefore， evaluation of the drug's inhibitory activity against the hERG potassium channel is a required step in drug discovery and development. In this study， we developed a series of novel conformation-mediated intramolecular photoinduced electron transfer fluorogenic probes for the hERG potassium channel. After careful evaluation， probes N4 and N6 showed good activity and may have a promising application in the cell-based hERG potassium channel inhibitory activity assay， as well as potential hERG-associated cardiotoxicity evaluation. Compared with other assay methods， such as patch clamp assay， radio-ligand competitive binding assay， fluorescence polarization and potential-sensitive fluorescent probes， this method is convenient and can also selectively measure the inhibitory activity in the native state of the hERG potassium channel. Meanwhile， these probes can also be used for hERG potassium channel imaging without complex washing steps.