This paper presents a method to develop an electronically controlled towing bar system, which will enable an autonomous agricultural vehicle to follow a leading tractor with a given lateral and longitudinal offset. In our study not only the follow-up motions but also the problems such as avoiding obstacle, turning at the end of the field have been considered. With the aid of the RTK GPS systems the position of the leading tractor can be obtained with accuracy in the range of centimetres. The position points of the leading tractor are transmitted by wireless modems to the following vehicle continually to provide the target position points for the guidance of the following agricultural vehicle. With the method of curve fitting a desired path for the following vehicle could be dynamically created. Based on the target position points and the path planning, the desired speed and the desired steering angle of the following tractor are calculated. In order to ensure the precise navigation of the driverless following tractor, a course tracking controller and a speed controller have to be designed and implemented. In addition to path tracking methods, considerations about safety of the towing bar system will also be issued in this paper. The whole research work is supported by the Federal Ministry of Food, Agriculture and Consumer Protection of the German Government.