Currently, the low self-harvesting efficiency of three-core cables has become a critical limitation for the application of online monitoring technology along cable routes. To address this issue, this paper proposes a novel magnetic field self-harvesting solution for three-core cables. Unlike traditional energy harvesting approaches based on the principle of transformers, this study innovatively proposes a magnetic field harvesting approach based on motor principles. This approach enhances the coupling between the core and the rotating magnetic field generated by the three-phase current, modifying the normal orientation of coil from tangentially parallel to the cable surface to radially parallel, and identifies the optimal energy harvesting position of device. The simulation results demonstrate that the approach proposed in this study yields higher open-circuit voltage and output power of coil compared to previous reported methods, thereby providing a significant enhancement of magnetic field self-harvesting efficiency. By combining finite element simulations with neural network algorithms, further analysis is conducted to assess the impact of parameters such as primary-current, material and dimensions of magnetic core on the open-circuit voltage of coils. Accordingly the optimization design strategies are proposed. Finally, a prototype is constructed and experiments are conducted in a laboratory setting. It′s found that the maximum output power is 2. 243 mW when the primary-side current is 50 A and three sets of coils possess 2 100 turns.