In order to realize the mutual towing and function optimization between different types of EMUs, the composition, control principle and shortcomings of the devices used to realize the return/rescue function of existing EMUs were compared and analyzed. Based on the fault-oriented safety, the function optimization was carried out, and the return and rescue conversion device integrating the rescue and rescued functions was designed and the vehicle control circuit was optimized. Experiments showed that the newly designed the return and rescue conversion device can meet the functional requirements and related standards of mutual rescue between different types of EMUs, and realize the functional integration and design optimization of the existing devices.