48 V i-BSG(intelligent belt driven starter generator) motor is one of the core parts in hybrid vehicle system. It has comprehensive functions of starting, generating, energy recovering and power assisting. Therefore, it can improve performance of low speed region of engine，which makes vehicle get better performance of emission and better fuel economy. In order to achieve excellent performance indicators, the design of motor’s electromagnetism is optimized with the finite element software. The motor working model and control strategy are expounded in detail. A motor prototype is manufactured and successfully passes the test verification. The results of experiment show that the motor can realize the design objectives. Compared with Valeo’s motor, it has the advantages of small volume and low cost, which lays a solid foundation for marketing.