The invention discloses a waterproof coiled-material base layer. The waterproof coiled-material base layer comprises a slope protection pile, slope protection anchoring steel beams, a keel and a pressure plate, wherein the slope protection pile is arranged at the slope of a foundation pit; the slope protection anchoring steel beams are horizontally fixed on the outer surface of the slope protection pile; the keel is implanted into the slope protection pile and supported and fixed by the slope protection anchoring steel beams, and gravels fill the keel; the pressure plate is laid on the outer surface of the keel. The waterproof coiled-material base layer has the advantages that the assembled waterproof coiled-material base layer uses square tubes as the keel, the square tubes are welded to the slope protection anchoring steel beams, and the outer-sealing cement pressure plate is used as the surface plate; the waterproof coiled-material base layer is safe, reliable, fast and convenient in construction, capable of saving construction cost, evident in actual application effect in the construction of a basement outer wall unilateral formwork waterproof project, and the like.