Vanadium oxide cluster cations VxOy+ (x = 2-6) are prepared by laser ablation and are reacted with D2O in a fast flow reactor under room temperature conditions. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Observation of the products (V2O5)(1-3)D+ indicates the deuterium atom abstraction reaction (V2O5)(1-3)(+) + D2O -> (V2O5)(1-3)D+ + OD. In addition, significant association products (V2O5)(1-3)D2O+ are also observed in the experiments. Density functional theory calculations are performed to study the reaction mechanisms of V4O10+ with H2O. The calculated results are in agreement with the experimental observations and indicate that H2O is dissociatively rather than molecularly adsorbed in V4O10H2O+ complex.