Reversible switching between superhydrophobic and superhydrophilic wettability of a polyamide film witha triangular net-like structure can be achieved by biaxially extending and unloading the elastic film. Both the change of the average side-length of the triangular net-like structure upon biaxial extension and unloading, and the surface tension of the water droplet, are believed to be responsible for the reversible switching between superhydrophobicity and superhydrophilicity.