Dating of shallow crusted faults has remained difficult. Although most brittle faults produce authigenic/synkinetic illite that can be used for radiometric dating， the fault gouges always retain detrital minerals， such as high-temperature 2M₁ polytype illite/mica that make the radioactive age data questioned. However， with the introduction of the Illite Age Analysis method and the "Age-Attractor" method， illite K-Ar/Ar-Ar ages of each grain size fraction can be used for constraining the activity time of near-surface brittle faults. This paper first introduces the principles and assumptions of illite dating， and then reviews the history of the study of fault gouge dating， including the principles and background of the Illite Age Analysis method and "Age-Attractor" method. Then， the factors affecting the dating of illite are evaluated， and it is believed that Ar loss is negligible in the near-surface brittle fault domain， and whether the 2M₁ polytype illite/mica is authigenic mineral is crucial for discussing the geological significance of illite age. Finally， it is pointed out that the illite dating method is not only used for shallow crusted fault dating， but can also constrain the deformation time of high-strain folds and tectonic mélange as well. In addition， if the main structural domains of subduction， accretion， and denudation in subduction zones are identified and dated， a complete temporal and spatial evolution process of the subduction zone can be obtained.