MD simulation of the layer-by-layer assembly of polyelectrolytes (PEs) and nanoparticles (NPs) revealed that the assembly process is electrostatically driven with alternating charge reversal and an overcompensation mechanism. Layers were observed to grow in the lateral direction as well as in a direction normal to the surface. Weakly adsorbed PE molecules were observed to desorb from the flat and NP surfaces. Those molecules are attracted by suspended NPs in solution. PE molecules do not Only Pull NPs toward the Surface but bridge NPs both in solution and on the surface, forming agglomerates and islands. The first double layer differs in structure from the second double layer as a result of strong adsorption of the PE molecules to the rigid surface.