In this article, an approximate analytical series solution of Modeling the pollution of a lake system is given. Laplace-Adomian decomposition method (LADM) was used for the serial solution. LADM with different input values has been used for the solution. The solutions obtained by LADM were compared with the results obtained by Fourth Order Runge Method. In addition, the results are compared with residual errors. These comparisons show that LADM is a powerful method for obtaining approximate solutions to the problem of modeling the pollution of a lake system.