The invention discloses a saturated dredger soft soil foundation reinforcing treatment system and a grid-type vacuum preloading and electroosmosis-method combined treatment method. The problems that when a saturated dredger soft soil foundation is treated with an existing vacuum preloading and electroosmosis combined method, the water content of saturated dredger soft soil in the construction initial stage is large, strength is quite low, and therefore workers and machines can not enter a site easily are solved. According to the treatment system and the treatment method, superficial-layer foundation treatment is carried out through a transverse water draining system and an electroosmosis system in the earlier construction stage, and deep-layer foundation reinforcing is carried out through a vertical water draining system in the later stage. Electrodes are vertically arranged, the electroosmosis flow direction of pore water and the vacuum osmosis flow direction of the transverse water draining system are overlapped accordingly, and the treatment efficiency of the vacuum preloading and electroosmosis combined method is improved to the maximum degree; and the superficial layer and the deep layer of the foundation can be reinforced through the arranging manner of the water draining systems. The treatment system and the treatment method have the beneficial effects of being convenient to construct, efficient in treatment and the like, electroosmosis and vacuum preloading are subjected to beneficial effect complementing, and the treatment system and the treatment method are suitable for reinforcing large-area saturated dredger soft soil foundations.