Objective  To investigate the social determinants that influenced the changes in the mental health of the rural-urban migrant population in Chengdu.

  Methods  Using data from two cross-sectional surveys, one conducted in 2009 and another, in 2018, of the rural-urban migrant population in Chengdu, we analyzed the social determinants of mental health affecting the rural-urban migrant population in Chengdu by multiple linear regression, and analyzed the contribution of changes in social determinants to the disparity in mental health over a decade using the Oaxaca-Blinder decomposition analysis.

  Results  This study included 3091 cases of rural-urban migrants in Chengdu, with 965 (31.22%) covered in the survey year of 2009 and 2126 (68.78%) covered in 2018. Multiple linear regression models were established with mental component summary (MCS) as the dependent variable, the social determinants of health as the independent variables, and gender, age, and survey year as covariates. The findings showed that being married (β=2.33, P<0.001), drinking 1-2 times per week (β=−1.42, P<0.05), illness within four weeks (β=−2.57, P<0.001), and hospitalization in the past year (β=−1.82, P<0.05), wage arrears (β=−1.67, P<0.05), job satisfaction (β=1.25, P<0.001), monthly housing costs (housing costs below monthly income: β=−1.55, P=0.001; housing costs above monthly income: β=−4.59, P=0.001) and housing condition (β=0.23, P<0.05) had significant impact on the MCS of the rural-urban migrant population. The results of the Oaxaca-Blinder decomposition method showed that the MCS disparity between the two surveys was −4.7660 points. With 2018 as the base year, the explainable parts accounted for 15.80%. Being married, decrease in the prevalence of illnesses within four weeks, and increased job satisfaction formed positive contribution to the improvement of the mental health, and increase in the proportion of monthly housing expenses formed negative contribution.

  Conclusion  Between 2009 and 2018, the mental health of the rural-urban migrant population in Chengdu showed improvement, and changes in marital status, illness within four weeks, job satisfaction, and monthly housing costs contributed to improvements in mental health during the period. Future intervention measures to promote the mental health of the floating population can be developed with the perspective of improving the social determinants of health in mind.