Exhaust purification system of internal combustion engine

An exhaust purification system of an internal combustion engine, the exhaust purification system comprising:na hydrocarbon feed valve for feeding hydrocarbons arranged inside an engine exhaust passage; andan exhaust purification catalyst, downstream of the hydrocarbon feed valve, for reacting NOx contained in exhaust gas and hydrocarbons which are injected from the hydrocarbon feed valve and are partially oxidized, whereinna precious metal catalyst is carried on the exhaust purification catalyst,a basic layer is formed on the exhaust purification catalyst,a top coat layer comprised of a hydrocarbon partial oxidation catalyst is formed on a bottom coat layer comprised of the exhaust purification catalyst, andthe exhaust purification catalyst has a property of:nchemically reducing the NOx contained in the exhaust gas when hydrocarbons are injected from the hydrocarbon feed valve at predetermined feed intervals while maintaining an air-fuel ratio of an exhaust gas flowing into the exhaust purification catalyst lean, andof being increased in a storage amount of NOx contained in the exhaust gas when the feed intervals of the hydrocarbons are longer than the predetermined feed intervals, andat the time of engine operation, a first NOx purification method that injects hydrocarbons from the hydrocarbon feed valve at said predetermined feed intervals while maintaining the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst lean so as to remove the NOx contained in the exhaust gas and a second NOx purification method that switches the air-fuel ratio of the exhaust gas that flows to the exhaust purification catalyst from lean to rich by intervals longer than said predetermined feed intervals to remove the NOx are selectively used in accordance with an operating state of an engine.