For the optimization design of magnetic coupling coil structure of wireless power transmission (WPT) system for electric vehicles, power level, transmission efficiency and economy should be considered comprehensively. The effect of number of coil turns and turn-spacing on transmission power, transmission efficiency and coil economy is analyzed first. Then, based on the non-dominated sorting genetic algorithm II (NSGA-II) with elitist strategy, a multi-objective optimization design method is proposed to optimize the coil parameters, such as number of coil turns and turn-spacing. The coil efficiency and coil economy are optimization objectives, and the 3.3 kW rated power and coil size are the constraint boundaries. Finally, based on the Maxwell-Simplorer co-simulation, the feasibility and validity of the optimization design method are verified. The maximum transmission efficiency of the optimized coil is 93.4%〖WTBZ〗, and the coil losses on both sides can be improved.