An exhaust purification system of an internal combustion engine comprising an exhaust treatment catalyst (13) arranged in an engine exhaust passage and a heat and hydrogen generation device (50) able to feed only heat or heat and hydrogen to the exhaust treatment catalyst (13). When the warm-up operation of the heat and hydrogen generation device (50) is completed and a reforming action by a reformer catalyst (54) becomes possible, if the temperature of the exhaust treatment catalyst (13) is a preset activation temperature or more, a partial oxidation reaction is performed at the heat and hydrogen generation device (50) and the generated heat and hydrogen are fed to the exhaust treatment catalyst (50). At this time, if the temperature of the exhaust treatment catalyst (13) is less than the preset activation temperature, a complete oxidation reaction by a lean air-fuel ratio is continued and a heat is fed to the exhaust treatment catalyst (13).