Abstract: Abstract：Evaluating the effects of economic developmental zones (EDZs) on regional economic development and revealing the spatial heterogeneity and mechanisms of these effects can provide useful guidance for coordinated development and optimization-upgrading of EDZs. Previous literature sparsely focus on the effects of EDZs on regional economic developments at the county level. Based on the panel data of the county-level regions of Hunan Provinces in China from 2001 to 2016, this paper uses the fixed-effect estimated models to examine the impacts of EDZs on the county-level regional economic development and spatial heterogeneity of these impacts. The results show that the establishments of EDZs have improved GDP and per capita GDP of the county-level regions, which mainly result from the two mechanisms of multiplier-effects and agglomeration-effects. More specially, the effects of the EDZs on the county-level regional economic development appear a feature of “increasing marginal effects”, that is, the higher the levels of economic development of the regions are, the stronger the role of EDZs to promote regional economic development becomes. The extent of the impacts of the EDZs relies on regional economic base.