Today, the unconventional policy of negative interest rate is discussed in many Western societies and developed countries, and the implementation of this policy in the financial and banking system has brought growth and prosperity in many economies involved in the crisis. In fact, by applying a negative interest rate, the bank will be able to direct credit allocation to productive and priority sectors. On the other hand, this policy, along with the independence of the central bank and the non-interference of the government in creating liquidity and making money from it, can reduce the level of inflation. Iran is a developing country with high inflation, and the interest rate as a monetary policy will not be very effective in the economy and is determined by the monetary authorities under the government's rule. When governments face budget deficits due to sanctions and lack of revenue sources, they create money by relying on their supervision over the performance of the central bank and use it as a solution to earn money, Therefore, it fuels inflation in the society. Therefore, in this research, within the framework of the optimization model of the money demand function and the model of money in the utility function, taken from the study of Walsh (2003) and Sidrauski (1967) and its extension, we will investigate the behavior of negative interest rates on inflation and optimal money interest. The obtained results show that in the environment of money interest and inflation, with the application of negative nominal interest rate, the equilibrium path has a downward and decreasing trend, and in this situation, inflation and money interest will decrease in the long term. Therefore, the government has the ability to compensate for its budget deficit through solutions such as bonds and income tax, and in the long term, by reducing the money interest rate, it can reduce the level of inflation in the society and this will improve the social welfare of people.
