Exhaust purification system for internal combustion engine

An exhaust purification system for an internal combustion engine comprises a storage and reducing type NOx catalyst (12) provided at an exhaust passage, an SOx absorbent (9) provided at an upstream side of the NOx catalyst (12), a reducing agent feeding means (60) provided at an upstream side of the SOx absorbent (9), and an S trap rate detecting means for detecting an S trap rate (Rs) of the SOx absorbent (9). In the exhaust purification system when the S trap rate (Rs) is smaller than a predetermined value (Rs0), the reducing agent is fed by the reducing agent feeding means (60), so that the amount of temperature change (Ta) of the SOx absorbent (9) before and after the feed of the reducing agent by the reducing agent feeding means (60) is made to become smaller than the amount of temperature change (Tb) of the NOx catalyst (12) before and after the feed of the reducing agent and the temperature (Ta2) of the SOx absorbent (9) before and after the feed of the reducing agent is made to become higher than an S trap rate increasing temperature (Ti) and is made to become lower than an S ingredient disassociation temperature (Tr) for disassociation the S ingredient from said SOx absorbent, thereby making the NOx catalyst (12) high in temperature and making the air-fuel ratio rich so that the SOx stored in the NOx catalyst (12) is released. Duo to this, S poisoning of the storage and reducing type NOx catalyst (12) is prevented by a simple configuration.