Porous carbonized polydopamine nanospheres encapsulated with Fe-0-dominated Fe3O4/Fe-0/Fe3C nanoparticles (Fe@C-PDA) were feasibly fabricated by a one-step pyrolysis of the Fe-PDA polymer, which was employed to activate persulfate (PS) toward degrading tetracycline (TC). The morphology, structure, chemical compositions and textural properties of the resulting catalyst were characterized systematically, and effects of catalyst dosages, PS concentration, inorganic anions (HCO3- and Cl-), natural organic matter and practical water body were studied in detail. The N-doping derived from C-PDA not only enhanced TC adsorption capacity, but also worked as active sites for PS excitation. Moreover, Fe@C-PDA displayed an excellent efficiency and stability in the 5th cycle tests. Electron paramagnetic resonance, classical radical scavenging experiments and X-ray photoelectron spectroscopy analysis disclosed that the active species in the system were identified as sulfate radicals (SO4 center dot-) and hydroxyl radicals ((OH)-O-center dot), and the variable chemical valences of Fe3O4/Fe-0/Fe3C nanoparticles as well as N-doping in the C-PDA nanospheres contributed to the outstanding catalytic activity. This work can provide new insight of making this kind of Fe-based materials as the promising catalysts for application in eliminating organic pollutants.