An exhaust purification system of an internal combustion engine has a selective reduction type NOX catalyst device which can hold ammonia and a storage reduction type NOX catalyst device which is arranged at an upstream side of the selective reduction type NOX catalyst device, which makes an air-fuel ratio of exhaust gas which flows into the storage reduction type NOX catalyst device change from a lean air-fuel ratio to a rich air-fuel ratio for starting an ammonia generation period, and which makes an air-fuel ratio of exhaust gas which flows into the storage reduction type NOX catalyst device change from a rich air-fuel ratio to a lean air-fuel ratio for ending the ammonia generation period.