Abstract: Integrating wireless power transfer (WPT) technology into pavement structure is an effective way to solve the inconvenience of electric vehicles (EVs) charging as supplementary for cable charging, accelerating the growth of ownership of EVs to adopt renewable energy and even achieve net carbon zero in the road transportation. In response to the problem that the distance between the coupling coils increases and the coupling degree decreases after the primary coil is embedded into the pavement structure, the coil structure was optimized to realize the wireless transmission of energy under large distance. The inner diameter, outer diameter and number of turns of the coil were optimized by electromagnetic finite element simulation, and the optimization process of the coil structure parameters with the coupling coefficient as the optimization target was proposed in the paper. Meanwhile, the circuit simulation platform of the WPT system was built in Simulink, and the performance of the WPT system with the optimized coil structure was tested. The results showed that with the increase of coil diameter, the coupling coefficient first increased to the peak and then decreased rapidly, and the coupling coefficient gradually increased as the outer diameter of the coil increased. The optimal number of turns of the coil was 9 turns for different outer diameters. Among the three coil parameters, increasing the outside diameter was the most effective way to improve the coil coupling degree. The final optimized parameters of the coil were the outer diameter of 480 mm, the inner diameter of 210 mm, and the number of turns of 9, which can achieve the power transmission at a distance of 300 mm. The output power of WPT system was maintained between 2.96 kW and 3.7 kW, and the transmission efficiency reached 86.54%. Then, the anti-migration performance of the coil structure was tested, and the allowable offset distance of the coil was up to 60 mm. The research provides theoretical support for the application of wireless charging technology for electric vehicles, and has strong engineering practical value.