The invention relates to an OBM-based road tunnel design method. The purposes are effectively achieved that the operation is convenient, the design precision and the modeling efficiency are improved,the size of a generated three-dimensional model is small, and the demands for splitting and data sorting of a later construction model are easily met. A tunnel three-dimensional terrain, a three-dimensional geological model are created, and tunnel surrounding rock division is conducted; a tunnel three-dimensional route model is established according to route design data; a tunnel cross section isdesigned, and a tunnel cross section template library is created; layout span lines are utilized for arrangement of surrounding rock pile numbers of a tunnel, and tunnel main hole, transverse channeland inclined well models are established; tunnel portal, portal side slope protector, steel bar, steel frame and tunnel anchor rod models are established; tunnel electromechanical, fire fighting, inner and outer prevention drainage and traffic engineering models are established; the transverse channel and main hole models are subjected to trimming modeling, a transverse channel is subjected to portal forming modeling in a main hole structure, the vehicle-passing transverse channel is subjected to sinking cable groove treatment, tunnel emergency stop widening modeling is conducted, and the tunnel model and the geological model are combined for modeling; the tunnel model is split, and tunnel components are coded.