Exhaust purification system for internal combustion engine

The present invention is a heat capacity than the exhaust purification apparatus in an exhaust passage of the upstream side of the exhaust purification apparatus small front end catalyst is formed, in the case where a reducing agent addition valve from the front reducing agent toward the upstream side end face of the catalyst addition, the front end catalyst and to inhibit the cut-out on a challenge. In the present invention, is the addition of the reducing agent is a reducing agent is added at a position that reaches the front end catalyst to the liquid valve is installed. And, when performing the addition of the reducing agent by the reducing agent supply valve for supplying the reducing agent on the front end catalyst and the exhaust purifying apparatus, when the activity level of the front end catalyst is higher than a predetermined level, if the active level of the front end catalyst is a predetermined level or less and more intensively than the reducing agent is added.