This study takes the central, provincial and municipal Environmental Protection Interviews (multi-hierarchical EPI) as a mechanism innovation for precise environmental regulation in Yangtze River Delta (YRD) and constructs a multi-cutoff regression discontinuity design to accurately measure the policy effects of multi-hierarchical EPI on air quality improvement in YRD. Overall, the findings demonstrate that EPI at all levels is correlated with improving the air quality for interviewed cities in the short term, which tends to weaken after 3–6 months and may even rebound to the initial level after a longer period. The improvement effect of EPI on air quality is primarily reflected in controlling the pollutant concentration of PM_2.5, PM₁₀ and NO₂. Moreover, there were great differences in the policy effects of the multi-hierarchical EPI for air quality improvement amongst cities in YRD. The higher administrative level of EPI, the stronger policy effects of the corresponding EPI were. The provincial and municipal EPI are likely to involve initiative regulation and exert greater effects. Some cities under the provincial and municipal EPI could break through the hierarchical constraints and shift to stronger air quality improvement effects, providing new reference for China's precise environmental governance mechanism.

本研究将中央、省、市环保访谈（多层次EPI）作为长三角环境精准监管的机制创新，构建多截止断点回归设计，准确测度多层次政策效果。 - 长三角空气质量改善分级EPI。总体而言，研究结果表明，各级 EPI 与受访城市的短期空气质量改善相关，3-6 个月后趋于减弱，甚至可能在较长时间后反弹至初始水平。_{EPI对空气质量的改善作用主要体现在对PM 2.5}、PM ₁₀和NO ₂污染物浓度的控制上. 此外，长三角城市间多层次EPI对空气质量改善的政策效果存在较大差异。EPI行政级别越高，相应EPI的政策效应越强。省、市环评有望主动调控，发挥更大作用。部分省市环评城市可以突破层级约束，向更强的空气质量改善效果转变，为我国环境精准治理机制提供新的借鉴。