Thin films of crystalline V2O5 nanoflakes were prepared through atomic layer deposition (ALD) process. The film thickness was verified to play a critical role in determining structural morphology, optical bandgap and Raman vibration of crystalline V2O5 thin films. Two optical bandgaps observed at about 2.8 eV and 2.4 eV result from two growth stages during ALD preparation. We expect that these results help to understand the growth control of ultrathin films and their functional devices.