The invention relates to a composite substrate suitable for artificially breeding ragworms and a construction method thereof and belongs to the technical field of aquiculture. According to the life habit of the ragworms and different proportions and thicknesses, pebble, fine sand, clay and the like with different grain diameters run through a coarse pebble layer, a fine pebble layer, a coarse sand layer, a fine sand layer and a clay mud layer in sequence from bottom to top to perform composite matching; and the thickness range of the composite substrate is between 50 and 100 cm. The composite substrate has high permeability and is suitable for the living of the ragworms and difficult to decay and deteriorate. A surface layer contains mass organic matters which can provide high-quality sufficient bait for the ragworms. Through detection, the composite substrate suitable for artificially breeding the ragworms and the construction method of the embodiment of the invention are used for breeding the ragworms; the survival rate of the breeding is up to 70 to 90 percent per year; and larvas with weight between 0.5 and 1.0 g can be up to about 10 g after one-year breeding. The body color of the ragworms is maroon; the heads of the ragworms have fluorescence; and the constitution is lusty.