Exhaust purification system of internal combustion engine

An exhaust purification system of an internal combustion engine in which a hydrocarbon feed valve for feeding hydrocarbons is arranged inside of an engine exhaust passage, an exhaust purification catalyst for reacting NOx contained in exhaust gas and reformed hydrocarbons is arranged inside of the engine exhaust passage downstream of the hydrocarbon feed valve, a precious metal catalyst is carried on an exhaust gas flow surface of the exhaust purification catalyst and a basic exhaust gas flow surface part is formed around the precious metal catalyst, the exhaust purification catalyst has a property of reducing the NOx which is contained in exhaust gas if a concentration of hydrocarbons flowing into the exhaust purification catalyst is made to 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 NOx which is contained in exhaust gas if the vibration period of the hydrocarbon concentration is made longer than the predetermined range, and, at the time of engine operation, at least one of an injection time and injection pressure of hydrocarbons from the hydrocarbon feed valve is controlled so that the amplitude of the change of concentration of hydrocarbons flowing into the exhaust purification catalyst becomes within said predetermined range of amplitude, an injection period of hydrocarbons from the hydrocarbon feed valve is controlled so that the concentration of hydrocarbons flowing into the exhaust purification catalyst vibrates by within said predetermined range of period, when only the injection time of hydrocarbons is controlled, the injection time of hydrocarbons under the same engine operating state is made longer the higher a temperature of the exhaust purification catalyst, and when the injection pressure of hydrocarbons is controlled, the injection pressure of hydrocarbons under the same engine operating state is made higher the higher the temperature of the exhaust purification catalyst.