The invention provides an offset intersection overpass with a preposed left turning for a crossroad. The overpass comprises a vertical lane, a transverse lane, a traffic lane, a left turning overpass, a left turning overpass entrance and a left turning overpass exit. The overpass is characterized in that the left turning overpass entrance of the vertical lane is elevated at the preposed position, an S-shaped turning spans the reverse traffic lane in the front of an exit of a reverse left turning overpass to move forwards along the sideway, an arc turning spans the reverse traffic lane of the transverse lane, and a downgrade is merged into a forward inside traffic lane; and left turning overpasses in other three directions are erected in the same mode. Compared with the prior art, the overpass with the preposed left turning for the crossroad has the advantages of compact integral structure, complete single layer, small influence to visual transparency and peripheral environment, low climbing slope for vehicles, less detour and small occupied floor area and space, is particularly applicable for urban central areas, downtown areas and landscape areas which require to improve the traffic speed but are deficient in dimensional elasticity. Therefore, the overpass has high popularization value.