The invention discloses a combined bridge consisting of two left-turn/straight-going bifurcate bridges in the shape of Bu (Chinese character). The combined bridge is in a combined structure which is composed of two independent bifurcate arch bridges and enables straight-going and left-turn motor vehicles traveling on 6-lanes on the opposite surface of a crossroad to have no cross road-occupying conflict. A left-turn bridge is positioned at the left side of a straight-going arch bridge so as to form a synclastically-bifurcate bridge in the shape of Bu (a Chinese character), and two synclastically-bifurcate bridges in the shape of Bu (a Chinese character) opposite to an intersection are formed into the combined bridge; and in the combined bridge, the one-way section of the straight-going arch bridge is positioned in the intersection of the opposite synclastically-bifurcate bridge in the shape of Bu (a Chinese character). The combined bridge disclosed by the invention has the advantages that the purpose that straight-going and left-turn motor vehicles traveling on the branch ground lanes of two 6-lanes on the opposite surface of a crossroad of a dual 6-lane have no cross road-occupying conflict can be achieved; and the degree of hazard (caused by local geological accidents) to the whole combined bridge is reduced; and the left-turn bridge can be used as a left-turn/right-turn shared bridge, so that the vehicles can directly turn left without redundant detouring.