为揭示建成环境与老年人步行活动之间的复杂关系，采用梯度提升回归树（gradient boosting regression tree, GBRT）模型，结合手机信令数据、遥感影像数据及兴趣点（point of interest, POI）等多源数据，深入探讨建成环境对老年人步行活动的非线性影响及其阈值特征。研究发现，建成环境对老年人步形活动的影响具有显著的非线性特征，其中土地利用要素的相对重要性最为突出，土地利用混合度、商业服务设施用地比例及居住用地比例是影响老年人步形活动的关键因素。此外，设施临近性也对老年人步行活动产生了重要影响。最后，提出了土地利用与设施的适老化改造建议，以提升老年人步行活动水平，促进健康老龄化。

To reveal the complex relationship between the built environment and walking activity among older adults, a gradient boosting regression tree (GBRT) model was adopted, combined with multi-source data such as mobile signaling data, remote sensing image data, and point of interest (POI), to deeply explore the non-linear impact of the built environment on elderly walking activities and its threshold characteristics. The findings indicate that the built environment has a significant nonlinear impact on older adults'walking activity, with land use factors being the most influential. Specifically, land use mix, the proportion of commercial service facilities, and the proportion of residential land are identified as key factors affecting older adults' walking activity. Additionally, the proximity of facilities also plays an important role. Finally, suggestions have been put forward for the adaptive transformation of land use and facilities to improve the level of elderly walking activities and promote healthy aging.