Mixed acid was used to make the functionalization of carbon nanotubes( CNTs) and rare earth( RE) treated CNTs( CNTs/RE) suspension was prepared. CNTs/RE self assembled monolayers ( CNTs/RE SAM) was fabricated on the single crystal silicon substrate by a self assembling process. The testing results of XPS spectra and SEM images indicated that after CNTs was functionalized, it contained hydroxyl, carboxyl groups. The surface treatment effect of CNTs was most obvious when RE concentration was 0. 3wt% . From the absorption spectra, we found that CNTs/RE SAM had absorption in the ultraviolet visible region, its absorption peaks were relatively in the ultraviolet region and the spectral response range of crystalline silicon solar cell wasexpanded.