The invention discloses a heavy truck duplex driving axle capable of achieving double speeds. The driving axle is composed of a middle axle assembly and a rear axle assembly, and is characterized in that a power transmission system of the middle axle assembly is composed of an input flange, an input shaft, an end cover, a box body, a planetary speed reducing device, a spline sleeve, a sliding meshing sleeve, a fixed support, an output shaft, an inter-axle differential assembly of the duplex driving axle, a driving cylindrical gear, a driven cylindrical gear, a driving bevel gear, a driven bevel gear pair, an inter-wheel differential assembly, a half shaft (19), a through shaft, an inter-axle transmission shaft and the rear axle assembly; a control system of the middle axle assembly is composed of a spline sleeve, a sliding meshing sleeve, a fixed support, a shifting fork and a reversing valve assembly. The driving axle has a speed change function, the use range of a truck is wider, andthe driving axle has the advantages of being simple and compact in structure, having few reversing elements, being high in transmission efficiency and the like.