In order to solve the problems such as low output voltage and current performance of traditional claw-pole generators, the performance research and optimization of vehicle-mounted claw-pole generator have been done. Based on the prototype data, the magnetic field model of the generator is built with 3D FEM, and the circuit model is built with SPICE. According to the parameter change curve in the traditional generator operation, the mathematical model is modified in the simulation; the results show the reliability of this built model. The simulation of this model without optimization under no-load and load are compared. From the change curve of the magnetic density at each point of the rotor, the geometric parameters in the claw pole model are optimized to explore the change of the induced voltage, and the voltage of the model with optimization is obtained. The prototype is produced and tested; the data is analyzed; the optimized model and the prototype can effectively improve the induced voltage and output current. The application of the three-dimensional field-circuit coupling in the claw-pole generator is verified.