An exhaust purification system for an internal combustion engine where combustion is performed under an excess of air, which exhaust purification system comprises: an NO x storage and reduction catalyst to be arranged in an engine exhaust passage, the NO x storage and reduction catalyst being configured to store NO x when an air-fuel ratio of exhaust gas which flows into said NO x storage and reduction catalyst is lean and to release stored NO x and reduce the released NO x to N 2 or ammonia when the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst becomes rich; an NO oxidation catalyst to be arranged downstream of said NO x storage and reduction catalyst in the engine exhaust passage, the NO oxidation catalyst being configured to oxidize part of NO in the exhaust gas which flows into said NO oxidation catalyst to NO 2; an NO 2 reduction catalyst to be arranged downstream of said NO oxidation catalyst in the engine exhaust passage, the NO 2 reduction catalyst being configured to reduce part of the NO 2 in the exhaust gas which flows into said NO 2 reduction catalyst to NO under an oxidizing atmosphere; and a selective reduction catalyst to be arranged downstream of said NO 2 reduction catalyst in the engine exhaust passage, the selective reduction catalyst being configured to hold ammonia in the exhaust gas which flows into said selective reduction catalyst and to selectively reduce NO x in the exhaust gas which flows into said selective reduction catalyst by said ammonia under an oxidizing atmosphere; characterized by: a controller which is configured to control the engine to temporarily switch the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst to a rich air-fuel ratio which is adapted for producing ammonia from NO x which is stored in said NO x storage and reduction catalyst, whereby the ammonia which is produced by said NO x storage and reduction catalyst is held by said selective reduction catalyst, and the NO x in the exhaust gas which flows into said selective reduction catalyst is reduced by said ammonia after the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst is returned to lean. an NO x storage and reduction catalyst to be arranged in an engine exhaust passage, the NO x storage and reduction catalyst being configured to store NO x when an air-fuel ratio of exhaust gas which flows into said NO x storage and reduction catalyst is lean and to release stored NO x and reduce the released NO x to N 2 or ammonia when the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst becomes rich; an NO oxidation catalyst to be arranged downstream of said NO x storage and reduction catalyst in the engine exhaust passage, the NO oxidation catalyst being configured to oxidize part of NO in the exhaust gas which flows into said NO oxidation catalyst to NO 2; an NO 2 reduction catalyst to be arranged downstream of said NO oxidation catalyst in the engine exhaust passage, the NO 2 reduction catalyst being configured to reduce part of the NO 2 in the exhaust gas which flows into said NO 2 reduction catalyst to NO under an oxidizing atmosphere; and a selective reduction catalyst to be arranged downstream of said NO 2 reduction catalyst in the engine exhaust passage, the selective reduction catalyst being configured to hold ammonia in the exhaust gas which flows into said selective reduction catalyst and to selectively reduce NO x in the exhaust gas which flows into said selective reduction catalyst by said ammonia under an oxidizing atmosphere; characterized by: a controller which is configured to control the engine to temporarily switch the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst to a rich air-fuel ratio which is adapted for producing ammonia from NO x which is stored in said NO x storage and reduction catalyst, whereby the ammonia which is produced by said NO x storage and reduction catalyst is held by said selective reduction catalyst, and the NO x in the exhaust gas which flows into said selective reduction catalyst is reduced by said ammonia after the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst is returned to lean. a controller which is configured to control the engine to temporarily switch the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst to a rich air-fuel ratio which is adapted for producing ammonia from NO x which is stored in said NO x storage and reduction catalyst, whereby the ammonia which is produced by said NO x storage and reduction catalyst is held by said selective reduction catalyst, and the NO x in the exhaust gas which flows into said selective reduction catalyst is reduced by said ammonia after the air-fuel ratio of the exhaust gas which flows into said NO x storage and reduction catalyst is returned to lean.