Faced with the ever-increasing energy demand in the world, the development of solar thermal systems is of interest to our Sahelian countries. Flat solar collectors convert the solar energy into thermal energy extracted by the air flowing through the collector. This conversion allows on the one hand the drying of agricultural products and on the other hand the heating of domestic water. In order to contribute to the improvement of flat solar collectors, we develop in this work a modeling and simulation of the thermal behavior of air in a glazed flat solar collector with two absorbers. The study is carried out from a mathematical model obtained from the energy conservation laws of the system. To solve the system of equations, we used the finite difference method with an implicit scheme. The algebraic system obtained is solved by the iterative Gauss Seidel method and the program is written in FORTRAN language allowing to generate from the input data, the temperatures of the various media of the collector. The results show that the different environments of the flat solar collector vary proportionally to the absorbed power and reach their maximum values in the period 13 h to 15 h. The maximum value of the upper air temperature is 62.21 °C. The average efficiency of the flat solar collector is 35.01%.