Polycrystalline black silicon with a periodic structure are fabricated by the combination of SiO2 nanospheres mask and reactive ion etching method. The damage layer is removed from energetic ion bombardment by dipping into a diluted NaOH solution, and the polycrystalline black silicon is optimized. Al2O3 thin film is deposited by atomic layer deposition method, and the samples are treated by rapid thermal annealing. Results show that damage layer could be removed completely by dipping into NaOH solution, and the nanostructure is smooth while maintaining the original black silicon structure. A balanced effect combining surface passivation and anti-reflectance are obtained after the rapid thermal annealing at 450 ℃. Minority carrier lifetime and effective surface recombination velocity are 29.34 μs and 306 cm·s-1,respectively. In the visible wavelength range, the average reflectance reduces to 7.12%.