<p>The misuse of fenitrothion (FNT) in food products poses a significant threat to human health, emphasizing the need for efficient and rapid analysis methods. This study presents a novel electrochemical sensor based on the biocarbon derived from sunflower seed shell/tin dioxide (SSS-BC/SnO₂) composite for rapid detection of FNT by square wave voltammetry (SWV). Simultaneously, a series of techniques were employed to characterize the morphology, structural, and electrochemical characterization of materials. SSS-BC is an environmentally friendly and economical carbon material compared to chemically derived carbon materials, and it has a large specific surface area, rich pore structure, fast electron transport capability, and is also an excellent carrier for SnO₂. The combination of the two materials effectively enhanced the catalytic effect on FNT. Under optimal conditions, the sensor exhibits a strong linear response to FNT in the concentration intervals of 0.004 ~ 20 and 20 ~ 120&#xa0;μmol·L⁻¹ with corresponding high sensitivities of 24.94 and 14.43 μA·μmol⁻¹·cm⁻², and the limit of detection (LOD) is 1.038&#xa0;nmol·L⁻¹ (S/N = 3). Additionally, this novel electrochemical sensor demonstrates excellent reproducibility and interference resistance, with average recoveries of grape samples ranging from 98 to 103%, similar to the results of high-performance liquid chromatography. In conclusion, this novel electrochemical method has the potential to efficiently monitor FNT residues in food products.</p>