We focus on highly grafted binary polymer brushes with compatible components in the cases of different chain lengths. Layered structures parallel to the surface that indicating "phase separation" are observed in a series of dissipative particle dynamics simulations. The stretch parameters indicate that the short chains are suppressed in the lower layer of the film, whereas the longer chains are much stretched in the region dominated by the short chains (lower layer) but possess relaxed conformations in the upper layer. By slightly changing the solvent selectivity to prefer the short chains, we find a reversion of the layered structure. Such a sensitive switch of film property implies its potential application as tuning the wettability and adhesion of the surface in industry.