An exhaust purification system of an internal combustion engine in which a hydrocarbon feed valve is arranged in an engine exhaust passage, an exhaust purification catalyst and a particulate filter are arranged downstream of the hydrocarbon feed valve in the engine exhaust passage, a precious metal catalyst is carried on an exhaust gas flow surface of the exhaust purification catalyst, a basic exhaust gas flow surface part is formed around the precious metal catalyst, the exhaust purification catalyst has a property of reducing NOx contained in an exhaust gas when making a concentration of hydrocarbons which flow into the exhaust purification catalyst vibrate within a predetermined range of amplitude and within a predetermined range of period and has a property of being increased in storage amount of NO X contained in the exhaust gas if making the vibration period of the hydrocarbon concentration longer than the predetermined range, and hydrocarbons are injected from the hydrocarbon feed valve within the predetermined period at the time of engine operation to thereby remove NO X contained in the exhaust gas, characterized in that: said exhaust purification system comprises a low pressure exhaust gas recirculation system which makes an exhaust gas in the engine exhaust passage downstream of the exhaust purification catalyst and particulate filter recirculate to an inside of an intake passage and an electronic control unit configured to perform the following steps: if hydrocarbons are injected from the hydrocarbon feed valve when an exhaust gas recirculation action by said low pressure exhaust gas recirculation system is performed, a carbon dioxide produced in the exhaust purification catalyst is recirculated and after the injection of hydrocarbons, each time the time which is required for recirculation of the carbon dioxide elapses, a temporary drop in an air-fuel ratio of an inflowing exhaust gas which flows into the exhaust purification catalyst and particulate filter is repeatedly caused, an injection of hydrocarbons from the hydrocarbon feed valve which is synchronized with the temporary drop in air-fuel ratio of the inflowing exhaust gas is allowed when hydrocarbons are injected from the hydrocarbon feed valve within said predetermined range of period for removing NO x which is contained in the exhaust gas, and hydrocarbons are injected from the hydrocarbon feed valve so as not to overlap with the temporary drop in the air-fuel ratio of the inflowing exhaust gas when hydrocarbons are periodically injected from the hydrocarbon feed valve for temperature elevation control of at least one of the particulate filter and exhaust purification catalyst. said exhaust purification system comprises a low pressure exhaust gas recirculation system which makes an exhaust gas in the engine exhaust passage downstream of the exhaust purification catalyst and particulate filter recirculate to an inside of an intake passage and an electronic control unit configured to perform the following steps: if hydrocarbons are injected from the hydrocarbon feed valve when an exhaust gas recirculation action by said low pressure exhaust gas recirculation system is performed, a carbon dioxide produced in the exhaust purification catalyst is recirculated and after the injection of hydrocarbons, each time the time which is required for recirculation of the carbon dioxide elapses, a temporary drop in an air-fuel ratio of an inflowing exhaust gas which flows into the exhaust purification catalyst and particulate filter is repeatedly caused, if hydrocarbons are injected from the hydrocarbon feed valve when an exhaust gas recirculation action by said low pressure exhaust gas recirculation system is performed, a carbon dioxide produced in the exhaust purification catalyst is recirculated and after the injection of hydrocarbons, each time the time which is required for recirculation of the carbon dioxide elapses, a temporary drop in an air-fuel ratio of an inflowing exhaust gas which flows into the exhaust purification catalyst and particulate filter is repeatedly caused, an injection of hydrocarbons from the hydrocarbon feed valve which is synchronized with the temporary drop in air-fuel ratio of the inflowing exhaust gas is allowed when hydrocarbons are injected from the hydrocarbon feed valve within said predetermined range of period for removing NO x which is contained in the exhaust gas, and hydrocarbons are injected from the hydrocarbon feed valve so as not to overlap with the temporary drop in the air-fuel ratio of the inflowing exhaust gas when hydrocarbons are periodically injected from the hydrocarbon feed valve for temperature elevation control of at least one of the particulate filter and exhaust purification catalyst.