Background: China is promoting the equalization of National Essential Public Health Services (NEPHS) for the internal migrants (IMs). Studies have analyzed the impact of migration range (MR) and regional economic development level (REDL) on the IMs' NEPHS utilization (NEPHSU), but no studies have explored the interaction of MR and REDL on it.Methods: Data from the China Migrant Dynamic Survey of 2017, involving 122656 IMs. Per capita GDP was set as the indicator for REDL, and 28 provinces were divided into three groups according to REDL: affluent, medium and poor. The MR was divided into inter-province and intra-province, and social capital (SC) was distinguished into cognitive (CSC) and structural social capital (SSC). Awareness of NEPHS (ANEPHS) and establishment of health record (EHR) were selected as indexes of NEPHSU. Multiple line charts and hierarchical logistic regression were used to investigate the interaction of MR, REDL and SC on NEPHSU.Results: (1) The socioeconomic status (SES) and social capital (SC) of inter-provincial IMs were significantly lower than those of intra-provincial IMs, and the gap was most prominent in affluent areas. (2) From low to high, the NEPHSU of inter-provincial IMs was ranked as affluent, medium and poor, while the corresponding order of intra-provincial IMs was medium, poor and affluent areas, and the gap of NEPHSU between inter-provincial and intra-provincial IMs was the largest in affluent areas. (3) SC could significantly promote the IMs' NEPHSU, but there was a gap between inter-provincial and intra-provincial IMs, and the gap was the largest in affluent areas.Conclution: REDL can significantly affect the gaps of SES and SC among subgroups of IMs with different MR. Inter-provincial migrants in affluent areas have relatively lower SES and SC, which may be a major barrier to their access to NEPHS, and the government should pay special attention to this vulnerable group when promoting equalization of NEPHS for IMs.