Single-polymer composites (SPCs), of which matrix and reinforcement are from the same polymer, are necessary for terms of resource recycling, energy conservation, and emissions reduction. In comparison with the traditional preparation process of fiber-reinforced polymer composites, the processing temperature window is the key technique to prepare SPCs due to the similar melting temperature of the matrix and reinforcement. Polypropylene (PP) SPCs have lightweight, low cost, easy recyclability, good interfacial adhesion, and better impact resistance. The preparation methods of PP SPCs included the hot compaction of fibers/fabrics, film stacking, co-extrusion compression, extrusion-calendering, injection molding, etc. The PP SPCs have been applied in automobile protective plates, bulletproof, luggage, sports, medical protective equipment, construction, etc.