Generally understanding of stimuli-responsive hydrogels is sol-gel transition under various stimulus. However, current knowledge from stimuli-responsive hydrogels always meets poor mechanical property with a gel state. Although the proposed method of hydrophobic effect usually introduced into hydrogels to design various types of tough hydrogel, the mechanically tunable hydrogel by stimulus response was rarely reported. Herein, a mechanically redox-tunable hydrogel driven by valent transformation between ferrous and ferric ions was designed and prepared. The mechanical strength of hydrophobic association hydrogels can be easily reduced by destroying metal complexation, due to the transformation from ferric to ferrous ions assisted by ultraviolet-sensitive citric acid molecules. Moreover, the mechanical strength of reduced hydrogels can be significantly enhanced through the reforming interaction between ferric ions and carboxylate groups of hydrdgels exposed to oxygen. It is envisioned that the mechanically stimuli-tunable strategy would provide new insights for designing the novel stimuli-responsive hydrogels. (C) 2017 Elsevier B.V. All rights reserved.