To emphasize the effect of humid or liquid circumstances on the mechanical behavior of metallic thin films with dimensions down to the nanoscale, atomistic simulations were employed to study the water film affecting the plastic deformation of Cu thin film during nanoindentation with different loading rates and indentation speeds. The results indicate that the largest load increases with the water film thickness and indentation rate for displacement-controlled indentation, contrary to the trend of the largest penetration depth for load-controlled indentation. The dislocation evolution reveals that the raised indentation speed or loading rate results in larger and rapider plastic deformation. The presence and thickening of water film as a media of force transmission from indenter to Cu thin film lead to a wide range of plasticity within Cu, large load dissipation and surface damage. The plastic deformation of Cu thin film under different indentation modes shows similarly changed trend. Our observations provide a better understanding of the mechanism of plastic deformation under the effect of water film. (C) 2017 Elsevier B.V. All rights reserved.