为检验波特假说与污染避难所假说在港口环境规制中的适用性，以中国船舶排放控制区政策（《船舶大气污染物排放控制区实施方案》（交海发〔2018〕168号））为准自然实验，选取不受政策影响的10个内河港口城市构建合成控制组，运用合成控制法对上海、宁波、舟山3个沿海港域2015—2025年月度面板数据进行实证分析。研究发现：①三港域PM_2.5浓度相对反事实路径分别下降5.7%、11.7%和5.1%，该效应在IMO 2020限硫令生效前的2019年窗口已完整显现，排除IMO 2020的独立驱动；②SO₂浓度已接近浓度地板（干预前为7.4~12.3 μg/m³），水平值效应无法与零区分，规制增量主要体现为PM_2.5协同减排；③宁波、舟山港域吞吐量相对反事实路径增长24.3%和44.8%，上海基本持平（-6.0%），未发现污染避难所假说预期的吞吐量转移，弱波特假说在扩张期港域获得支持，增长阶段是调节两类效应的关键维度。建议将考核分为两层：执法层核验燃油硫含量，效果层锚定PM_2.5，将其纳入船舶排放控制区常态化考核核心指标；基准按增长阶段差异化设定，扩张期以排放强度降幅不低于吞吐量增速为达标线，成熟期以排放总量稳定下降为达标线。

To test the applicability of the Porter Hypothesis and the Pollution Haven Hypothesis in the context of port environmental regulation, this paper took China′s Domestic Emission Control Area (DECA) policy—Implementation Scheme of the Domestic Emission Control Areas for Atmospheric Pollution from Vessels—as a quasi-natural experiment. Ten inland river port cities completely unaffected by the policy were selected to construct a synthetic control group, and the synthetic control method was applied to a monthly panel dataset (2015-2025) covering the coastal port areas of Shanghai, Ningbo, and Zhoushan. The results showed that: ①PM_2.5 concentrations in the three port areas declined by 5.7%, 11.7%, and 5.1%, respectively, relative to their counterfactual paths; this effect had fully materialized in the 2019 window prior to the entry into force of the IMO 2020 sulfur cap, thereby ruling out IMO 2020 as an independent driver; ②SO₂ concentrations were already close to the floor level (7.4~12.3 μg/m³ before the intervention), and the level effect was statistically indistinguishable from zero, indicating that the incremental effect of the regulation mainly took the form of synergistic PM_2.5 abatement; ③cargo throughput in Ningbo and Zhoushan grew by 24.3% and 44.8%, respectively, relative to the counterfactual paths, while Shanghai remained essentially flat (-6.0%); no throughput transfer anticipated by the Pollution Haven Hypothesis was observed, and the weak Porter Hypothesis was supported in growth-stage port areas, with the growth stage emerging as a key moderating dimension of both effects. It is recommended that the assessment framework be divided into two tiers: at the enforcement tier, the sulfur content of marine fuel should be verified, and at the effectiveness tier, PM_2.5 should be anchored as a core indicator in the routine assessment of DECA; benchmarks should be differentiated by growth stage—port areas in the expansion phase should be required to reduce emission intensity at a rate no lower than throughput growth, while those in the mature phase should be required to achieve a stable decline in total emissions.