This article analyzes the relationship between Government size and corruption. Unlike the works in the way which suppose a linear relationship between the two variables, we estimate a panel with change of the modes to characterize the impact of the size of the Central Government on corruption, in the countries of the economic community and monetary of Central Africa (EMCCA). The results show that there is a non-linear relationship between these two variables. Indeed, a strong involvement of the Government in economic activity results in a significant increase in corruption when the Government exceeds a size of 13.5508% of the GDP.