The exhaust purification system of an internal combustion engine of the present invention is provided with an NOX storage reduction catalyst and a particulate filter which is arranged at the upstream side of the NOX storage reduction catalyst. When causing the NOX storage reduction catalyst to release the stored NOX, the particulate filter is raised to the temperature at which the particulate matter is oxidized, the flow rate of the exhaust gas which flows into the particulate filter is made to decrease, the air-fuel ratio of the exhaust gas which flows into the particulate filter is made rich, and the particulate matter which builds up on the particulate filter is made to oxidize to produce carbon monoxide.