EXHAUST PURIFICATION SYSTEM OF INTERNAL COMBUSTION ENGINE

An exhaust purification system of an internal combustion engine 1 comprises a catalyst 28 arranged in an exhaust passage 27 of the internal combustion engine, a fuel supply device supplying fuel to the catalyst through the exhaust passage, and a control device 80 configured to control the supply of fuel by the fuel supply device. The control device is configured to calculate a concentration in exhaust gas of fuel supplied to the exhaust passage by the fuel supply device and a saturation vapor pressure concentration of the fuel and supply fuel from the fuel supply device to the catalyst only if the concentration in the exhaust gas is higher than the saturation vapor pressure concentration.