Refractory depression （TRD） is widespread， but there is no fully accepted definition of TRD. The difference of definitions is mainly in the specific provisions， the core point of view is the same， that is， it is lack of satisfactory effect for one or several adequate antidepressant treatments. At present， the most commonly used definition methods for TRD is two ineffective full dose and full course treatment. This review summarizes the concept of TRD， the different methods used to define TRD and their shortcomings in order to better understand TRD.