Large scale of ZnO seed layers were grown on the HD glass substrate by an electrodeposition method, after that, a hydrothermal growth of ZnO nanocrystals on the seeded substrate was performed. The obtained nanocrystals were characterized by FESEM, XRD, PL and photocatalytic test. The FESEM images indicate that the ZnO nanocrystals grown on ZnO-seed-coated substrate are flower-shaped. All the ZnO nanocrystal has a very good crystallinity with hexagonal wurtzite structure. We found that the preparation of the structure and morphology of ZnO nanocrystal can be controlled by changing the preparation parameters. While the hydrothermal temperature is the main factor that controls the morphology of nanocrystal, the hydrothermal time, the concentration of the solution also have an effect on the morphology. Its photo-degradation rate of methylene blue can reach 91% which is almost 1.5 times than the ZnO powder. (C) 2015 Elsevier B.V. All rights reserved.