Abstract: Due to the advantages on system efficiency, vehicle control and platform development, electric vehicles distributed driven by in-wheel traction machines have become a hot point. By comparing the distributed and concentrated driving topologies, this paper points out the great development potential of in-wheel traction machines. The researches in the field of machine topology innovation are described, and it is revealed that high torque density is the main developing direction. Besides, the researches on vibration, thermal management and optimization algorithm are concluded, while a global optimization technique considering multi-physical coupling needs to be explored. In the aspect of control technology, researches are focused on high-performance control and fault-tolerant control for the single-machine layer, and multi-machine cooperative control for the vehicle layer. Finally, this paper comprehensively summarizes the research progress of in-wheel traction machines and points out the technical directions in this field.