Heteroatoms doped carbon materials are widely used in the advanced oxidation process (AOPs) to remove organic pollutants in water due to the synergies effect between different heteroatoms. In this study, a novel kind of N, S co-doped magnetic mesoporous carbon nanosheets (Fe@NS-C) was prepared by simple one-step pyrolysis. Further, the influence of doping amount of S (L-methionine) and N (melamine) on catalytic activity was studied, the optimized sample Fe@NS-C-2-12/PMS showed a satisfying degradation ( 91.07%) for high concentrations of tetracycline (80 mg/L TC) in 10 min, which was attributed to the proper ratio of S content to N content (S(at.%)/ N(at.%) = 0.2097) in the sample could better play its synergistic effect by XPS analysis. The Fe@NS-C-2-12/ PMS system also exhibited satisfactory degradation effects in a wide pH range (3−10) and the existence of inorganic ions and humic acid. Then, the degradation mechanisms were mainly through the non-radical pathway (1O2 and electron transfer) and the major active sites were pyridinic N compared to thiophene S, CO, and Fe-Nx. This study could inspire the design of high-performance active and low-cost heteroatomic doping nano-magnetic catalysts for PMS-based waste treatment.