Since the creation of money, a good reading of inflation evolutions is an essential element for many economic actors. However, inflation as measured by the consumer price index represents some volatility. Indeed, since its establishment, the general price index shows a marked seasonality and its level rises irregularly. Therefore, It is essential for a central bank to distinguish in the evolutions of the inflation between what is simply noise , destined to disappear quickly, what is a sustainable trend. In the context of price stability that have adopted the aim of their monetary policy, central banks should control and have an accurate measure of structural inflation, namely the component corrected by the influence of economic cycle, because it is this element that is monetary origin. This component of inflation, called core inflation is obtained by canceling the cyclical component attributed to shocks on output. We try in this work to measure the main component of inflation in Tunisia from a structural VAR. The results comfort the choice of the approach because the calculated core inflation seems broadly in compliance with that waited on the theoretical plan.