Today, corruption is considered as one of the most effective factors in determining the economic status of countries, therefore, in this article, we use the data of 37 developing Islamic countries to investigate the relationship between the size of government and corruption in these countries using We have studied the FMOLS method between 2010 and 2020. Results showed that there is an inverse relationship between corruption and government size, so the main hypothesis of this study "there is a relationship between corruption and government size in selected countries" is not rejected. The bigger government size will lead to a decrease in the corruption index and therefore there will be more corruption in the country.