<p>Although the relationship between economic development and the environment has been extensively explored, systematic and in-depth research remains lacking on whether and to what extent economic growth has decoupled from ecological and environmental pressures. To address this gap, this study integrates a 1-km resolution Modified Remote Sensing-based Ecological Index (MRSEI) with the Tapio decoupling model to reveal the “Economy-Environment” interaction in the Beijing-Tianjin-Hebei (BTH) region from 2000 to 2020. Results show significant ecological improvement, with the average MRSEI rising from 0.386 in 2000 to 0.542 in 2020. Spatially, “Excellent” and “good” ecological zones expanded by 1.51 × 10⁵ km² combined, while degraded areas shrank significantly. Furthermore, the region has transitioned into a stable “weak decoupling” state, indicating that ecological degradation is slowing down relative to economic expansion. Scientifically, this study establishes MRSEI as a robust air–land integrated monitoring framework, overcoming the atmospheric blindness of conventional surface-based ecological indices and enabling more comprehensive regional assessments. Practically, the identification of spatial economy–environment conflict zones facilitates a transition from uniform regional regulations toward more targeted and differentiated ecological management approaches for areas under greater development pressure.</p>