Abstract: The long carbon fibers were opened and prepared for the fiber-mat by means of needling, and then were used to produce the carbon fiber-mat reinforced polypropylene composites(CFRPP) with continuous double steel belts press. Effects of the length of the carbon fiber, fiber content, needling and needling type, matrix modification on the mechanical property of the composite materials were discussed, and the surface properties of the composites were characterized by scanning electron microscopy(SEM). The results revealed that the fiber length had little influence on the mechanical properties of CFRPP within the experiment range. The carbon fiber content of composites with optimized comprehensive mechanical properties was about 30%. The tensile properties of composites were improved significantly when the carbon fiber was acupunctured by triangle needles. The compatilizer MPP can modify the interaction between carbon fiber and polypropylene, and thus improve the mechanical properties of composites. The optimized dosage of compatilizer MPP was about 20%. When the carbon fiber felt was made by triangle needling with fiber length of 80 mm and impregnated by polypropylene modified with 20% of MPP, the tensile strength of composite with fiber content of 30% reached 203.3 MPa, tensile modulus 16.6 GPa, flexural strength 223.2 MPa, flexural modulus 12.0 GPa, and the notched impact strength 752.2 J/m.