Mental health inequality is a major manifestation of health inequality in the psychological dimension, and it has become a realistic problem to challenge common social progress. The aim of this study is to review the domestic and international research on the measurement and decomposition of mental health inequality. The authors mainly discussed 3 aspects: socio-economic and demographic inequalities in mental health, and the impact of acute major infectious diseases on mental health inequality. They also summarized the commonly used indicators and research methods. This paper reviews the selection of data indicators, research subjects, and research perspectives, so as to provide evidence for further research on mental health inequality in China.