Subsurface wetland with effluent N/P suitable for culturing non-toxic green alga

The invention relates to a subsurface wetland with effluent N/P suitable for culturing non-toxic green alga. The subsurface wetland comprises a treating pond, wherein a water inlet and a water outlet are respectively formed in front and rear parts of the treating pond; the inside of the treating pond comprises a wetland plant layer, a soil layer and a packing medium layer from top to bottom sequentially; the packing medium layer is divided into a front treatment zone, an intermediate treatment zone and a rear treatment zone according to the water current direction; and the front, intermediate and rear treatment zones respectively contain zeolite and steel slag in different proportions. Compared with the prior art, the subsurface wetland has the advantages that wastewater which is substandard after secondary treatment is subjected to oriented deep treatment; the structure is simple, blockage is prevented and management is convenient; the total nitrogen concentration of effluent is 8-12mg/L, the total phosphorous concentration is 0.4-0.5mg/L, and N/P is 20-30. The water quality of treated water is beneficial to control of eutrophication of receiving water from the source and has a certain economic value by means of ecological reclamation; moreover, after the secondary treated wastewater is further treated by virtue of the subsurface wetland, COD is further reduced.