Disclosed is a bidirectional transmission control system for a vehicle. A road identification device collects an image of a road on which a vehicle is currently travelling, and after identifying the type of the road on which the vehicle is currently travelling according to the road image, forwards a corresponding first terrain mode request signal via a signal relaying device to an all terrain controller so as to start a corresponding terrain mode under an all terrain adaptation mode. In addition, the terrain controller forwards execution information about the terrain mode via the signal relaying device to the road identification device so as to realise state feedback of the terrain mode currently executed. The invention can coordinate the inconsistency of information transmission rates between an all terrain control system of a vehicle and an input system, thereby aiding in real time switching of various terrain modes.