We discuss high-field magnetic properties of the quasi two dimensional frustrated dimer spin system SrCu2(BO3)2, which is a realization of the Shastry-Sutherland spin model and shows magnetization plateaus at 1/8, 1/4 and 1/3 of the saturated magnetization. Based on the results of 11B NMR experiments, we discuss (1) the spin superstructure in the plateau phases, (2) the effects of anisotropic interactions such as the Dzyaloshinski-Moriya interaction, and (3) nature of the phases above the 1/8 plateau.