BackgroundHealth inequality caused by the scarcity and uneven distribution of paediatric service resources is common worldwide. The hospital strategic alliance may improve paediatric service capacity and health equity, but this hypothesis has not yielded consistent results. Here, we examine the hospital strategic alliance’s effect on local hospitals’ paediatric service capacity.MethodsThe paediatric monitoring data of 119 local hospitals from 14 cities between 2015 and 2019 were obtained from the Hubei Pediatric Quality Control Center and the Provincial Statistical Yearbook. We employed the difference-in-differences model with multiple periods. The samples were divided into three groups—close cooperation group, loose-knit cooperation group and control group—differentiated by hierarchical clustering based on the implementation of core initiatives. The number of outpatient visits and the number of inpatient visits were used as the outcomes. The ‘available beds’ and the ‘health personnel per 1000 resident population’ were chosen as the control variables.ResultsThe cross-over Treat×Post coefficient was significantly positive at a 1% level in Models 1 and 3, with or without control variables. Specifically, the coefficient for the number of outpatients in Model 2 was significantly positive at the 5% level, supporting Hypothesis H1. Model 4 confirmed a significantly positive cross-over Treat×Post coefficient at a 1% level, and Model 3 showed a larger coefficient than Model 2, indicating greater benefits for the loose-knit cooperation model, supporting Hypothesis H2.ConclusionsThe hospital strategic alliance enhanced the paediatric service capacity of local hospitals. Furthermore, the close cooperation model appears to be a more effective solution for addressing health inequality caused by the scarcity and uneven distribution of paediatric service resources.