The invention relates to an internal combustion engine and provides a repeated pressure boosting internal combustion engine which can separately complete an energy conversion process and is high in energy utilization efficiency, low in fuel consumption rate and high in speed, torque and power. According to the main principle of the repeated pressure boosting internal combustion engine, the suction process, the compression process, the acting process and the exhaust process are separately conducted in two air cylinders which are different in size, effective pressure in the air cylinders is increased at the time of acting through self structures, as a result, the combustion process is improved, and thermal efficiency is also improved; moreover, matched with a turbocharger, a compression air cylinder 2 can suck in more air in a high speed stage to support the combustion of fuel. The repeated pressure boosting internal combustion engine has the advantages of being simple in structure, high in thermal efficiency, wide in operation adjustable range, low in oil consumption, good in acceleration performance, sufficient in power at a low speed, and strong in power at a high speed; moreover, acting frequency is doubled, the rotating speed range is substantially expanded, and therefore vibrations are reduced; due to the supercharged effect after combustion, the combustion process is improved, the fuel can be combusted more sufficiently and thoroughly, and the emission performance is better.