BackgroundEnhancing the pooling of basic medical insurance plays a vital role in strengthening the resilience to risk and co-payment capacity of medical insurance funds. In China, there is a concerted effort to shift from municipal to provincial pooling of medical insurance. While existing research suggests that provincial pooling of basic health insurance affects the health of participants, the findings are not yet consistent, and there is limited research on the specific pathways of impact between the two. Therefore, this study aims to explore the influence of provincial pooling of basic medical insurance on participants' health and analyze the mediating role of medical cost burden and medical service utilization.MethodsUsing data from the 2012–2018 China Labor Dynamics Survey (CLDS), this study focuses on a sample of urban workers enrolled in basic medical insurance. After excluding samples with missing information, a total of 5,684 participants were included in the analysis. The effects of the provincial pooling policy of basic medical insurance on participants' medical cost burden, medical service utilization, and health were analyzed using double difference modeling. Furthermore, structural equation modeling was employed to explore the mediating paths between provincial pooling and health.ResultsThe findings reveal that provincial pooling of basic medical insurance significantly impacts participants' medical cost burden, medical service utilization, and health. Specifically, provincial pooling helps reduce the participants' medical cost burden (β = -0.1205;P< 0.001), improves the level of medical institutions visited (β = 1.7962;P< 0.001), and promotes health improvement (β = 1.8370;P< 0.001). The mediating effect analysis demonstrates that the direct effect of provincial pooling on health is 1.073 (P< 0.001), with a mediating effect of medical cost burden between provincial pooling and health measuring 0.129 (P< 0.001). Heterogeneity analysis indicates that provincial pooling is more effective in reducing the burden of medical costs for low-income (β = -0.2273;P< 0.001) and high-age participants (β = -0.2710;P< 0.001), and it also helps increase the burden of medical costs for low-income (β = 4.0875;P< 0.001) and high-age participants (β = 1.9010;P< 0.001) based on provider ranking. Moreover, it is found that provincial pooling is more beneficial in improving the health of high-income (β = 1.7984;P< 0.001) and middle- and high-age enrollees (β = 1.9220;P< 0.001; β = 0.5900;P< 0.001). Further analysis reveals that the provincial unified income and expenditure mode has a more positive effect than the provincial risk adjustment fund mode in reducing the medical expense burden of the insured (-0.2053 < -0.0775), improving the grade of medical institutions (1.8552 > 0.8878), and enhancing the health level (2.8406 > 0.6812).ConclusionThe study concludes that provincial pooling of basic medical insurance has a direct positive impact on participants' health and indirectly promotes health improvement by reducing the burden of medical costs. The effects of provincial pooling on participants' medical cost burden, medical service utilization, and health vary based on income and age. Additionally, the provincial-level unified collection and payment model proves to be more advantageous in optimizing the functioning of health insurance funds through the "law of large numbers" principle.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12939-023-01927-1.