The utility model discloses a paper diaper with a composite core structure. The paper diaper comprises punched non-woven fabric, an absorbing core, a composite breathable film and a retaining wall for preventing side leakage. The paper diaper is characterized in that the absorbing core body is composed of two layers, namely a composite core and a cotton core; the composite core is composed of puffing paper layers in the upper layer, high molecular water-absorbing resin layers in the middle and fluffy cotton layers in the lower layer; and the high molecular water-absorbing resin layers are uniformly embedded between the puffing paper layers and the fluffy cotton layers, and the layers are bonded through a hot melt adhesive. The paper diaper with the composite core structure has the functions of high absorption, low back leakage, no broken cotton and no lumping.