Large, high quality single crystals of Dy2Ti2O7 have been successfully grown by the floating zone technique in an infrared image furnace. The obtained single crystal has been characterized by X-ray diffraction at room temperature and is shown to have the face centred cubic structure, Fd3m, with a room temperature lattice parameter a＝1.0112(2) nm. The full-width at half-maximum of rocking curves of ［111］ and ［400］ Bragg peaks are 0.07° and 0.05°, respectively. Magnetic susceptibility measurements give a Van Vleck paramagnetic parameter of 2.46×10-5m3/mol, the effective moment μeff＝10.24(4)μB and Cure-Weiss temperature ΘCW＝1.1 K, indicating weak ferromagnetism for the Dy2Ti2O7 single crystal. The comparative studies of the experiment and theoretical analysis reveal that the long-ranged dipole-dipole interactions dominate the magnetic behaviors of this kind of spin ice system, and the dipolar energy scale Dnn=3.00 K.