The objective of this research is to determine the factors that explain the long-term evolution of variation in Congo. To do this, we implemented an error-corrected vector model (EVCM) over a long period of time (1980-2019). The results obtained show that political instability and the evolution of the price of oil are the two main factors that explain, respectively by 16.9% and 12.8%, the evolution of long-term variation in Congo. Thus, to enable the Bank of Central African States to properly play its role of preserving the price level, within the limits of the Community rule of an inflation rate not exceeding 3% per year in force in the Economic and Monetary Community of Central Africa (EMCCA), it is important to maintain the stability of the political situation and diversify the national economy.