Herein, Fe(III)-doped g-C3N4 (FeCN) could efficiently activate peroxymonosulfate (PMS), which was prepared via a facile one-pot synthesis approach. The physical and chemical properties of the samples were characterized by XRD, FTIR, SEM, TEM, XPS, and BET. The FeCN/PMS system displayed high activity in the degradation of several contaminants, including cationic rhodamine B (RhB), anionic methyl orange (MO), and neutral phenol. Compared to SO4 center dot--based advanced oxidation technology, the FeCN/PMS system is a nonradical process; high-valent iron-oxo species (Fe-IV = O) and singlet oxygen (O-1(2)) are the primary reactive oxygen species (ROS). The effects of various operational parameters, such as catalyst loading, peroxymonosulfate dosage, substrate concentration, and pH, on the performance of the FeCN6/PMS system were also studied. FeCN6/PMS exhibited acceptable degradation of RhB in the presence of coexisting anions (i.e., Cl-, SO42-, NO3-, and H2PO4-) and natural organic matter (NOM).