The surface strength of expanded polypropylene (EPP) products can be improved and their service life extended through the application of coatings. However, developing coatings with high adhesion to unmodified EPP materials remains a challenge. In this study, polypropylene-grafted-amine (PP-g-NH2) was used as a modifier and crosslinking agent, and a waterborne polyurea (WPUA) was prepared by introducing hydrophilic monomer dimethylolpropionic acid (DMPA) into the polyurea molecular chain using a prepolymer method. The aim was to improve the poor adhesion of the polyurea coating to the foamed polypropylene (EPP) substrate. Fourier transform infrared spectroscopy (FT-IR) confirmed the successful incorporation of PP-g-NH2 into the WPUA molecular chain.The effect of PP-g-NH2 content (mass percentage of PP-g-NH2 relative to the total mass of modified WPUA raw materials) on the adhesion, contact angle, solvent resistance, mechanical properties, and thermal stability of WPUA was investigated. The study found that introducing a 1.5% mass fraction of PP-g-NH2 into the system resulted in enhanced membrane properties. The modified membranes exhibited a water absorption capacity of 14.52% and a contact angle of 84.85°, outperforming unmodified EPP. Additionally, the modified membranes showed improved tensile strength (30.6 MPa) and elongation at breakage (233.7%). Furthermore, the thermal decomposition temperature of the modified membranes increased by 20℃and the adhesion to EPP reached 0.89 MPa, representing a 65% improvement compared to unmodified polyurea.