The invention discloses a high-efficient intake and exhaust system of an internal combustion engine, wherein a cam of a gas distribution mechanism is an eccentric cam, and a profile of the eccentric cam consists of a base line, an opening profile, a closed profile and a deep-stroke line. The high-efficient intake and exhaust system disclosed by the invention has the advantages of suitability for large, intermediate and small cylinders, a single cylinder and multiple cylinders, a water-air-cooled engine, increased power due to natural air suction (preferably boosted intermediate cold) and full combustion, low oil consumption, low exhaust reaching the Europe emission standard 1-4, low noise, low vibration, low idle speed, low cost, long service life, good startability and reliability, and reduced oil consumption and emission compared with the same model of the internal combustion engine, and is an upgrade product that the energy is saved by 20 percent and the emission is reduced by 50 percent; and the internal combustion engine with performances exceeding the advanced level of the world and various matched powers are obtained.