The invention discloses polypropylene composition. The polypropylene composition is characterized by comprising components in parts by weight as follows: 80-85 parts of PP-1, 10-15 parts of PP-2, 5-10 parts of maleic anhydride grafted polypropylene, 6-10 parts of ethylene-propylene copolymers, 5-15 parts of ethylene-octene copolymers, 5-20 parts of HDPE (high-density polyethylene), 20-35 parts of talc, 0.1-1 part of a coupling agent, 0.5-1.0 parts of an antioxidant, 0.1-0.3 parts of an anti-ultraviolet agent and 1-3 parts of pigments, wherein PP-1 is out-of-phase polypropylene, and the melt flow rate MFR2 of PP-1 is not smaller than 100g/10 min at the test temperature of 230 DEG C under the load of 2.16 kg and is measured according to ISO (international standard organization) 1133; PP-2 is crystalline noblen, and the melt flow rate MFR2 of PP-2 is not larger than 15g/10 min at the test temperature of 230 DEG C under the load of 2.16 kg and is measured according to ISO 1133; the melt flow rate MFR2 of HDPE ranges from 5g/10 min to 8g/10 min at the test temperature of 190 DEG C under the load of 2.16 kg and is measured according to ISO 1133. The invention further discloses a preparation method of the polypropylene composition.