The invention discloses a farmland ecologic interception ditch adopting a slope protection technology and a construction method of the ditch. The cross section of the channel takes the shape of an inverted trapezoid, a ditch bottom is a prefabricated perforated plate, S-shaped holes are arranged in a staggered manner, and local perennial aquatic plants are planted in the holes; after being compacted, the soil bodies of ditch walls are paved with three-dimensional plant nets and covered with prefabricated perforated plates, a plurality of holes are in parallel and uniformly distributed at the middle upper parts of the perforated plates, wire grass is planted in the holes, and rye grass is replanted in the holes; a water inlet end is provided with a grating, and a water outflow end is provided with a controllable emptying gate. Through the reasonable arrangement of the plant planting holes and the anchoring action of root systems and the plant cover nets, the structural stability of the ditch is achieved. The ecologic interception ditch provided by the invention has the advantages that the structure is stable, the structural stability can approximately reach the structural strength of a concrete ditch built in facility grainfield, water erosion of farmland drainage can be resisted effectively, and meanwhile suspended matters, nitrogen, phosphorus and the like in drain water of farmland, particularly dry land, are effectively intercepted; no cultivated land is occupied, the construction cost is low, the operation is simple, and suitability for large-scale popularization and application is achieved.