The utility model relates to the technical field of foundation treatment in wetland areas, in particular to a plastic plate type drainage device for foundation treatment in a wetland area. Due to the fact that the problems of insufficient strength, poor stability, deformation, leakage and liquidation can appear when a building is constructed on a soft foundation in a wetland, the soft foundation in the wetland needs to be treated. According to the plastic plate type drainage device, connecting ribs are arranged on the edges of a plate body, and connecting grooves are formed in every two adjacent edges; a drainage port is formed in the plate body and is communicated with a water storage tank through a groove; supporting ribs are welded to the groove through which the drainage port is communicated with the water storage tank; reinforcing ribs are arranged in the drainage port. By the adoption of the plastic plate type drainage device for foundation treatment, drainage consolidation of a soft layer can be improved remarkably, and a whole project can be conducted smoothly.