The invention discloses a suspension device for a mining dump truck, which comprises a cylinder barrel and a piston rod barrel. The inner side of the piston rod barrel and the inner side of the cylinder barrel form a cylinder barrel oil cavity; the lower end of the piston rod barrel is sleeved with a piston; the upper end of the cylinder barrel is provided with a cylinder sleeve; the inner side of the cylinder barrel and the outer side of the piston rod barrel form a ring-shaped oil cavity; and the ring-shaped oil cavity is connected with the cylinder barrel oil cavity through an internal damping hole and an internal damping one-way valve passage respectively which are formed on the piston rod cylinder. The suspension device is characterized in that: the outer side of the cylinder barrel, which is close to the internal damping hole, is provided with an external damping mechanism; an external damping oil cavity is formed in the external damping mechanism; an external damping one-way valve passage divides the external damping oil cavity into an upper oil cavity and a lower oil cavity; the upper oil cavity is communicated with the ring-shaped oil cavity through a through hole; and the lower oil cavity is communicated with the cylinder barrel oil cavity through the external damping hole, the external damping hole is arranged below the idle load travel of the piston and above the full load travel. The external damping mechanism is arranged, so the suspension device can meet the requirements of a vehicle on rigidity and damping performance under idle load and full load working conditions.