Abstract: The traditional claw-pole machine control air-gap flux to transmit stable output voltage to batteries by regulation excitation current,which has disadvantages such as lower output capacity and inefficiency caused by leakage flux.It doesn’t meet the current requirements of hybrid vehicle power supply.A hybrid excitation claw-pole belt-starter-generator（BSG） machine for 42 V power supply system hybrid electric vehicles（HEVs） has been created.Through permanent magnets inserted among claws,this kind of generator can reduce the leakage between the claw-poles,increase machine power density and output capacity under low speed.This paper will use magnetic circuit and three-dimension finite element methods to analyze the structure and principles of BSG.The multi-domain simulation methods include mechanism,vibration modal and thermotics to solve the analysis of high-density machine ultimate capacity and optimization.The simulation results have showed that with high starting torque in starter mode,the machine can constantly provide output voltage at wide speed range for batteries charging in generator mode.Experimental results of prototype confirm the theoretical analysis and simulation conclusion.The prototype has advantages such as low leakage,large output capacity and hard output characteristics,which has broad application prospect for hybrid electrical vehicles.