EXHAUST PURIFICATION SYSTEM OF INTERNAL COMBUSTION ENGINE AND EXHAUST PURIFICATION METHOD

An exhaust purification system of an internal combustion engine comprises an HC adsorbent arranged adsorbing HC in exhaust gas, an NOx adsorbent adsorbing NOx in exhaust gas, a catalyst removing HC and NOx at a predetermined air-fuel ratio, an air-fuel ratio control part configured to control an air-fuel ratio of exhaust gas, and an HC concentration calculating part configured to calculate a concentration of HC desorbed from the HC adsorbent. A peak of a desorption temperature of HC at the HC adsorbent and a peak of a desorption temperature of NOx at the NOx adsorbent are substantially the same. The air-fuel ratio control part is configured to control an air-fuel ratio of inflowing exhaust gas flowing into the catalyst to the predetermined air-fuel ratio based on the concentration of HC calculated by the HC concentration calculating part when HC is desorbed from the HC adsorbent.