BackgroundEnhancing health intervention for floating populations has become an essential aspect of public health around the world. China launched a policy reform aimed at implementing immediate reimbursement for trans-provincial inpatient treatments. The objective of this study was to investigate the effects of this policy change on socioeconomic inequality in health among the floating population.MethodsThis study used two waves of individual-level data from the China Migrants Dynamic Survey (CMDS) collected in 2017 and 2018 as well as administrative hospital data at the city level. The sample included 122061 individuals and 262 cities. Under a quasi-experimental research design, we built up the framework to employ the generalized and multi-period difference-in-differences estimation strategy. We used the number of qualified hospitals that could provide immediate reimbursement to represent the degree and intensity of the implementation of this policy change. We also calculated the Wagstaff Index (WI) to measure socioeconomic inequality in health.ResultsThis policy change and income level had a negative joint impact on the health status of floating population (odds ratio = 0.955,P< 0.01), that is, the lower the income, the better the number of qualified hospitals' effect on health improvement. Furthermore, as the number of qualified tertiary hospitals increased, the health inequality would decrease significantly on average at the city level (P< 0.05). In addition, inpatient utilization as well as total expenditure and reimbursement significantly improved after the policy change, and the magnitude of increase was greater in the relatively lower-income group (P< 0.01). Finally, only inpatient spending could obtain immediate reimbursement in the early stage, thus, compared with primary care, these impacts were greater in tertiary care.ConclusionsOur study revealed that after the implementation of immediate reimbursement, the floating population could obtain greater and more timely reimbursement, which significantly increased its inpatient utilization, promoted health, and reduced the health inequality caused by socioeconomic factors. These results suggest that a more accessible and friendly medical insurance scheme should be promoted for this group.