The monetary policy affects on economy by several channels. The most important are Interest rate channel, exchange rate channel and credit channel. In interest rate channel case, decreasing in money supply cause to increase interest rate and so investment is decreasing and it causes the diminishing of production. But in exchange rate channel, decreasing in money supply cause to increase interest rate and so, the rise of attractiveness domestic banking facilities. Following this situation, export prices start to rise and so, export and national production decrease. The function of credit channel is that decreasing in money supply cause to decrease bank deposit and following that, banking facilities diminish and it causes investment and production decrease. In this article, we try to study the function of credit channel. In other words, the effect of monetary policy on banking facilities, credits and liquidity has been studied. The results of this study show that monetary policy index (legal deposit rate) has negative effect on banking facilities and credit growth rate. So the existence of credit channel in Iran has accepted. But, as this effect is so little, the result of this monetary policy index would not be acceptable in policy making.