The purpose of this study is to investigate the determinants of inflation in the period 1960- 2011 and autoregressive model (VAR) is used here. In this study due to the structure of the Iranian economy, the mark-up index is derived and its growth along with liquidity growth, nominal exchange rate growth and productivity growth are used in the model. The results of Granger causality test show one-way causal relationship between the three variables of mark-up growth, exchange rates growth and labor productivity growth in one hand and inflation on the other hand, as well as two-way causal relationship between money growth and inflation. Also impuls response functions confirm a negative relationship between labor productivity growth and inflation. Moreover, based on the analysis of impulse response functions of three variables of mark-up growth, liquidity growth and exchange rate growth, they are positively correlated with inflation. Variance decomposition showed that each of the variables of inflation, mark-up growth and labor productivity growth in the short-term and respectively with the shares of 45, 29 and 25 percent, have the highest explanation on inflation forecast variance. But in the long run, the effect of mark-up growth is reduced, and labor productivity growth, inflation, liquidity growth, exchange rate growth and mark-up respectively explain 30, 28, 17, 14 and 10 percents of the forecast errors.