Abstract: Herbicide safeners are a group of compounds with special purpose which can selectively protect crop plants from the phytotoxicity of herbicide without reducing the toxicity to target weeds. Clarifying the action mechanism of safeners will help the development of new safeners. According to the present research, there are four major hypothesis about the action mechanism of safeners:1) affecting the uptake and translocation of herbicide in crops, 2) competing the binding sites with herbicide, 3) affecting the activity of herbicide on the target enzyme, 4) strengthening the metabolism of herbicides in crops. The progress of the action mechanism of safeners and the effect of safeners to weeds were summarized. The current unsolved problems and the future research directions are pointed out, which may provide evidences for the further research of safener action mechanism and promote the development of new safeners.